It's the Emperor's. The seed of other men have no effect on Ray. Petri is effectively impotent because of the seal on his body, and Oran is also effectively impotent because of some other thing (it was mentioned in passing).
Basically the Emperor's bloodline is one of the few that can impregnate Ray (because of his strong mana, lesser seed just die off).
he is an assassin who consumed alot of poison back in the day, thats caused the infertility
that's what it was xD thank you very much
Also, the wizard created a potion to allow conception to happen. It was used with the emperor, and probably wouldn't have worked otherwise
Uhm to ask is it really his majesty those kids or did Ray lied to him about it?...