The family's roots originate in Odessa in the Russian Empire (present-day Ukraine), but they were driven out by two pogroms in 1859 and 1871 because of their Jewish faith. They resettled in England in the 1860's, where they acquired both the title of Sinderby and built a successful banking business, through which in turn they built a massive fortune. The grandfather of the present Lord Sinderby chose to change the family's name to Aldridge. Daniel Aldridge and Rachel Aldridge became Lord and Lady Sinderby after they moved to the Yorkshire village of Sinderby (hence their title). Ripon is mentioned to by the halfway point between Sinderby and Downton.
The Aldridges are related to the MacClare family through Atticus Aldridge's marriage to Lady Rose MacClare, the youngest daughter of Hugh MacClare, Marquess of Flintshire. The family remains staunchly Jewish, with the exception of Rose, who is Anglican.
Daniel Aldridge and his wife Rachel are the present Lord and Lady Sinderby, and are important figures among England's Jewish population. Lord Sinderby in particular is proud of all his family has accomplished and also of his Jewish faith. They mention having several cousins, while they themselves have one son and heir, Ephraim Atticus Aldridge. Lord Sinderby has also fathered an illegitimate son, also named Daniel, by his mistress Diana Clark.
Atticus becomes engaged and marries Rose MacClare in 1924.
- Lord Sinderby mentioned that any children Atticus has with Rose will be born Anglican, but Atticus says that they may still choose to convert to Judaism.
- The family's original name before it was changed remains unknown.