When I was in the Army 25 years ago, I read a series of 3 books about an alien race of feline humanoids that were slaves to an advanced race of lizard humanoids. The main character was bought as a pet for the daughter of an emperor. They were friends as youths but the main character escaped and started a rebellion. The daughter became empress and both became mortal enemies. I remember the main character had a litter and the empress was baring eggs in the final battle. I also remember mentions and characters of other races in the universe of the books. It was a trilogy and I think the title had alien in it but I’m not sure about that part. I would love to read these books again. This has bothered me for years lol. Thank you