Owlstar opposes the addition to warrior code, suggested by Featherstar of WindClan, forbidding outsiders from the Clans. It was rumored that he had kittypet ancestry, but Leafpool says this is false and that he sees that the Clans will be weakened if non-forestborn cats are purged from all Clans. He insists that as long as cats are loyal to their Clan, they deserve to stay.
It's been revealed that the Owlstar from Secrets of the Clans and the Owlstar from Code of the Clans are two different cats.
"Owlstar of ThunderClan argued most strongly against her. It was rumored afterward that he had kittypets among his ancestors, but he didn't. He just saw that all the Clans would be weakened if they had to purge their members of non-forestborn cats. Loyalty to Clanmates has always lain at the core of the warrior code, and what Featherstar was proposing would let Clanmates turn on another and claim superiority for something they had no control over."