Miss Sybil Patricia Branson, II (always called "Sybbie" to differentiate her from her late mother and her namesake) is a child character in the PBS/ITV period soap, Downton Abbey. She was played as a two year old toddler by Ava Mann, but was played as a four year old by child actress, Fifi Hart.
Tom and Sybil's daughter....and the first Crawley grandchild
Sybil, always called Sybbie, is the daughter of Tom Branson, the former chauffeur of the Crawley family and Lady Sybil Crawley Branson, the youngest daughter of The Earl of Grantham and The Countess of Grantham who was herself a practicing nurse. We first meet her in the fifth episode of the third season after she was born.
Sybbie was born at Downton Abbey, the only one of the three grandchildren who was born at the ancestral home of the Crawleys. Her cousin, Georgie, was born at Downton Cottage Hospital, the village's hospital; and her youngest cousin, Marigold, was born in Geneva, Switzerland.
She is always called Miss Sybbie, and as she grew, she would still be called Miss Sybbie, as her father, Tom Branson, wasn't titled (and a former servant). However, her place in the hierarchy would never be fully delineated.
It is presumed that since the entail law (which bedeviled her family as her granny's fortune had been tied into the estate) had been finally abolished, and should something had happen to her cousin, George, slated to be the 8th earl, there is a chance, she could inherit as she was the eldest granddaughter.
However, by the time she grew up, there wouldn't have been any real delineation anyway, as she would always be a Crawley (due to her mother); and yet be a Branson (due to her father).
Her birth occurred after the fanfare filled visit of her maternal great-grandmother, Martha Levinson, whom her paternal great grandmother would derisively consider, "That Woman".
Sybbie's birth, Sybil's death
Sadly, only mere moments after her birth, her mother died of pre-eclampsia. The medical fights over whether mother and child would survive a caesarean section nearly drove a wedge in the family. The practicing OB/GYN, Sir Phillip Tapsell, and Downton's physician, Dr. Richard Clarkson, who had known Sybil from when she was an infant, were arguing about how to handle things.
Because of Tapsell's arrogance, he ignored the signs of Eclampsia, and that led to Sybil's untimely death. Cora outright blamed her husband and Tapsell for her death, scorning him because "he was knighted, fashionable and had an office in Harley Street, and you would ignore the findings of a man who had known Sybil since she was born!"
Because of that, she banished Robert into his dressing room, allowing her to mourn Sybil by herself.
Later on, Dr. Clarkson would be manipulated by Violet to tell them that there was only a very small chance that Sybil would have survived. Although the lie was well-intentioned and was told in order to bring the family back together, it was still a lie. Clarkson reluctantly allowed himself to be involved that way.
After her mother's death, Tom would step up and become a hands on father to his little girl, although, like most aristocratic children of that era, she was raised mainly by nannies. He absolutely adored his daughter, and to him, his first priority, no matter what, was always Sybbie. To him, his world clearly revolved around his little girl.
When Sybbie was first cast, with Ava Mann playing her, she looked a lot like Sybil with the same hair color as her mother but when the role was recast with Fifi Hart, she was made to look a lot more like Tom, with her hair color nearly the same as his.
Because she and George (and later Marigold) lost one of their parents shortly after their births (George and Marigold lost their fathers; while Sybbie lost her mother), this bonds the children (more notably, George and Sybbie) closer than anything, and that makes them almost akin to siblings.
In a reversal of how Lady Mary Crawley and Lady Edith Pelham were due to their close ages (a lot of animosity), George and Sybbie are also close because they are only a year apart in age. Sybbie and George would find more comfort in each other, much like twins would be. As they grew together, they would became best friends.
When she was two, one nanny, a woman named Miss West, was sacked by her doting grandmother, Cora, after the woman had insulted her, by calling her a wicked cross-breed, which her granny overheard (This explained why Sybbie did not like Ms. West, as she would cry when the nasty nanny was around her).
Needless to say, she was canned on the spot. The now ex-Nanny West was crying all the while she was packing. Cora then engaged a new nanny, one who clearly did not mind about Sybbie being who she was. Servants who served those who once were servants (as Tom used to be a chauffeur) would often be disgusted by that, but the new Nanny realized that Tom was now a part of the family.
When she was an infant, she gained a friend in the Abbey's butler, Charles Carson, who had overheard the child crying. Going into the nursery, the usually autocratic and humorless butler showed his hidden heart of gold when he picked her up and comforted her.
He took her into the library so she would calm down. When the family's housekeeper, Mrs. Hughes, saw them as she was returning from an outing with the other household staff, she was touched. Admonishing her not to be sentimental, although he was indeed sentimental, Carson said that baby Sybbie reminded him of her mother (and her namesake), Lady Sybil, when she was her daughter's age.
As she grew, she gained the tendency to be a peacemaker, much like her parents were. She also gained the compassion that her mother had when she was alive. Due to Tom and Sybil both being rebellious, it is possible that Sybbie will gain that same kind of rebelliousness. Tom would also expose Sybbie to her Irish heritage, while she also would learn about her aristocratic heritage from her mother's family.
While everyone adored her, she was perhaps closest to her maternal grandmother. Cora was the first one in the family to call her Sybbie. She also was closest to her eldest granddaughter, as she saw her as the most tangible link she had to her late youngest daughter.
Sybbie and "Donk"
Sybbie adores her grandfather, but she had a quite unusual name for him. Due to a game of Pin the Tail on the Donkey that they had played together, Sybbie had taken to calling Robert, the Earl of Grantham, "Donk". At first he resisted it, hoping that she would call him something dignified like "Grandpappa" (he did not want George to call him Donk), but the rest of the family, including his mother, found it amusing. Bowing to public pressure from the family, he gave in to the nickname. He would later embrace the name, even going so far as to call himself "Donk".
Like her father, Sybbie is a Catholic, as she had been christened as such. Despite the protests of Robert, the christening went off without a hitch. It had been a request of Sybil, a request honored by Cora and Mary, that Sybbie be baptized as a Catholic. Although she was upset about it, Violet was more open to it, as a friend of hers was also, as she said, "more Catholic than the Pope."
Her aunt Lady Mary Crawley is the most important female figure in her life, aside from her grandmothers, as she is not only her aunt, but she is also her Godmother. She would encourage her niece to stand up for herself against those who would hurt her. She would also call her niece "darling" just as she had with her mother, when she was alive.
Her godfather is her uncle, Kieran Branson, a course and rough man whom Violet (whom she knew as "Granny Violet") disparagingly calls a "drunken gorilla". She called family cousin, Isobel Crawley Grey, "Aunt Isobel", as she was her great aunt (her late uncle, Matthew Crawley, was Isobel's son).
Despite her aristocratic heritage, Sybbie was like any ordinary four year old little girl, in that she was precocious, sweet, polite and very curious. She would usually be carrying around her favorite stuffed animal, her plush bunny.
She also enjoyed the times she spent alone with her father. They would go for walks around the abbey grounds, and at times, even to the annoyance of her nannies, he would steal up to the nursery to kiss her good morning and show her that he loved her very much.
He did this, knowing how he remembered the way his mother showered her love on her children, and Tom hoped that he could replicate that love he got from his mother and instill that into Sybbie.
He named her Sybil after her mother, because he wanted to be reminded of his late wife when he saw her. Although it was hard at first, he decided on Sybil as it was the only tangible connection to his late wife. In that way, Tom, Cora and Mary had common ground. Mary, Cora and Tom adored Sybil, and as such, Sybbie was the common link that they had to the youngest Crawley daughter.
Sybbie also had a champion in Thomas Barrow, her father's former comrade in service. He had a close friendship with Sybbie as well, due to the friendship and comradeship that he had shared with her late mother.
Robert had thought it ghoulish that he would name the child after her late mother, but both Cora and Mary disagreed with him. They found that with her being named after Sybil that it would be a good tribute to the youngest Crawley.
Robert, as was his wont to do with anything, was always trying to take over in Sybbie's upbringing, often insisting that what positives Sybbie had would be because of Sybil's aristocratic blood, and nothing about Tom's side of the family would be worth considering.
However, Tom also had formidable help in Cora and Mary who let Robert know that he did not know Sybil's wishes as he thought he did, and that also those wishes came into play, whether he liked it or not. And to also remind him that TOM was the father, and Robert was not.
He also did not like the idea of Sybbie being baptized as a Catholic (his mother, Violet Crawley had no liking for it either, although she was more amenable to it, as a dear friend of hers was Catholic), but, again, Mary and Cora overruled him, as it had been Sybil's wish to have her daughter be baptized as a Catholic like her father.
Mary revealed to Robert that on the day Sybil died, she made her wishes for her baby to be known that he or she (as it turned out, she) would be christened as a Catholic. He muttered about being flabbergasted, to which Cora said, "You're always flabbergasted by anyone doing the unconventional!"
Tom, Cora and Mary felt that Sybil's wishes were not being taken into consideration by Robert and Violet. In fact, at the christening, Robert and Violet were very unnerved when they had a picture taken with the priest who had christened Sybbie. During the christening, it would be when Tom, as a christening present from Sybil, would become Downton's new Estate Agent, replacing the previous agent, Jarvis.
Almost a mirror image of her parents
Sybbie was a lot like her late mother (both her parents really) in that she wanted things to be peaceful, and she was there to comfort those she cared about. An obvious example was when she comforted Robert's dog, Isis as she was dying of cancer.
She (and George) had a close friend in Thomas Barrow, the abbey's under-butler. His love for the children was one of the few redeeming features that the usually vindictive man had.
When he left, temporarily, in the final episode, Sybbie was there to help George during the times he missed his best friend, "Mister Barrow". As the two grew up, George and Sybbie had one other to lean on in tough times.
It was presumed that when she grew up, Sybbie would find her métier in a world that had well opened up for her. As she grew, she would turn to Mary, Cora and Edith for advice as her mother was long gone. She also had George to confide in.
She would, like her mother and aunts before her, have a season in London (it was presumed that she would be introduced by her aunt, Mary). She would also perhaps get married, as like most aristocratic young girls would be expected to, but the world that her mother and family knew was long gone by the time she became a young woman. As they say, the world was her oyster and Sybbie Branson would clearly find her own role in it.