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 the title of Sinderby and built a successful banking business, through which in turn they built a massive fortune. The present Lady Sinderby's ancestors are mentioned as arriving in England during the reign of Richard III.
Daniel and Rachel Aldridge became Lord and Lady Sinderby after they moved to the Yorkshire village of Sinderby (hence their title). Ripon is mentioned to be the halfway point between Sinderby and Downton. Their residence is the estate of Canningford Grange, which they renovated using their enormous wealth.
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. He moves with her to New York the following year, and by the end of 1925 they had a daughter named Victoria Rachel Cora.