Family

A family was a relationship between people by birth, marriage, adoption, or an especially strong friendship. Indeed, Sarah Jane Smith told the Tenth Doctor that he had the biggest family on Earth. (TV: Journey's End)

Those in a family were typically described as "relatives"; those that lived prior to an individual were known as ancestors, while those that lived after an individual were known as descendants.

The Doctor
The Doctor once had a family, but had lost them "a long time" before their thirteenth incarnation. (TV: The Woman Who Fell to Earth)

Indeed, the First Doctor had at least three grandchildren, Susan, (TV: "An Unearthly Child", et al.) John and Gillian, (COMIC: The Klepton Parasites, et al.) and the Tenth Doctor recalled having once been a father. (TV: Fear Her, The Doctor's Daughter) The Doctor's children were "sons or daughters, or both." (PROSE: The Eleventh Tiger)

The Doctor may have had a human mother, (TV: Doctor Who, PROSE: The Infinity Doctors) a Time Lord father, a grandfather, (PROSE: Cold Fusion) and indeed sisters. (TV: Arachnids in the UK) Irving Braxiatel was the Doctor's brother.

Another account suggested that he only had forty-four cousins, as he was loom-born. (PROSE: Lungbarrow, Celestial Intervention - A Gallifreyan Noir) The Eighth Doctor could not recall which origin was a dream, and which was real. (PROSE: The Shadows of Avalon)

The Eighth Doctor was also the adoptive father of Miranda Dawkins, (PROSE: Father Time) and Jenny was the Tenth Doctor's daughter via progenation. (TV: The Doctor's Daughter)

Raxacoricofallapatorious
Raxacoricofallapatorian families used hyphenated surnames. One family, the Slitheen, functioned as a criminal organisation in what Jocrassa Fel-Fotch Passameer-Day Slitheen refered to as a "family business". (TV: World War Three) This put them at odds with other families such as the Hostrozeen, the Blathereen, and the Hazrateen, who the Slitheen knew as cousins. (TV: Revenge of the Slitheen, AUDIO: The Taste of Death)