|Married to Rose Aldridge|
Canningford Grange, Yorkshire (formerly)
Rose Aldridge (wife)|
Victoria Rachel Cora Aldridge (daughter)
Daniel Aldridge (father)
Rachel Aldridge (mother)
Hugh MacClare (father-in-law)
Susan MacClare (mother-in-law)
Atticus's paternal ancestors came from Russia but were driven out because of their Jewish faith. They resettled in England where they acquired a massive fortune (by building a successful banking business) and the title of Sinderby. His great-grandfather changed the family name to Aldridge. Atticus's father considered changing the name back but never did, because the family felt they were English now and wished to stay that way.
His mother referred to him by his middle name rather than his first since he was a baby, and so he has gone by Atticus instead of Ephraim ever since.
Atticus meets Rose during a rainstorm, helping her with her bags. He continues to see her, and eventually reveals to her his and his family's Jewish faith, a fact which does not bother her.
Rose eventually introduces Atticus to her family, and he in turn introduces them to his parents. His mother finds Rose quite charming and is happy that Atticus is quite taken with her, whereas his father does not wish for him to marry out of the faith.
When Edith runs away, Rose lets Atticus in on the secret if he promises not to pass it on (despite the family's plan not to tell anyone). Atticus remembers Lord Grantham saying Edith had inherited Michael Gregson's publishing company. Atticus suggests contacting the office as they might know where to find her. Rose praises him as clever.
Atticus soon proposes to Rose, and she accepts. Rose's father takes a liking to Atticus. Unfortunately, Atticus's father and Rose's mother do not approve. When Lord Sinderby reminds his son that if he marries Rose their children will grow up Anglican, Atticus responds that they may choose to convert to Judaism in the future, and insists that any children he and Rose have will grow up knowing both faiths.
Susan tries to sabotage the wedding by setting Atticus up with a prostitute during his stag party. Atticus confronts his father, demanding to know if he was responsible as Atticus had not let Rose or any of her family know the extend of his father's disapproval. Lord Sinderby insists he was not responsible. Fortunately, Rose and Atticus go ahead and are happily married.
Atticus and Rose spend their honeymoon in Venice, Italy. They later join Atticus's parents and the Crawley family at Brancaster Castle in Northumberland for the grouse season, along with Lord Sinderby's butler Stowell. Later, Atticus and Rose announce plans to move to New York, where Atticus has gotten a job.
At Christmas that year, Rose and Atticus are back at Downton. Rose helps Atticus get used to the customs of Christmas, a holiday he himself never actually celebrated, helping him with singing carols. He tells her he finally feels that he belongs to two families, and she tells him that's what being married is all about. In January 1925, Rose and Atticus move to America.