Clio's father was the ruler of his planet.
When Clio turned five, she was poisoned by her Uncle Ferdand on behalf of his son Malvek, ruler of Dolmara. The First Doctor put Clio into stasis, and she was woken every year. At first, her father was present when she awoke, but later he did not appear. No one explained to Clio why he wasn't present. (PROSE: The Glass Princess)