Ruth Clayton's parents

"Ruth Clayton", a Chameleon Arch identity of the Doctor, remembered having parents who lived in a disused lighthouse around Gloucester.

According to Ruth, her relationship with them was strained. They died sometime after she moved away, and where buried nearby. They left the lighthouse to their daughter, who never wanted to live there.

Their grave, marked by a blank tombstone near the lighthouse, was actually where the Doctor's TARDIS had been buried. (TV: Fugitive of the Judoon)