Mritig was a Tractite who lived on the planet Paratractis in an alternate timeline where humanity never evolved on Earth. He was the son of Kitig and Narunil and the younger brother of Critil.
Mritig also had a twin sibling named Jontil. When the Eighth Doctor and Sam Jones visited Mritig's timeline in 2109, Mritig played tag with them in the garden outside the family's home. (PROSE: Genocide)