Does your Uncle eat chicken? In which case- is he worried that bit of karma will catch up with him? The reason chickens are bred and kept in terrible conditions and then slaughtered is so we can eat them. Just by living, we all inflict suffering on other living beings.
But no, I don't have much belief in reincarnation. I don't think it's impossible but, I just can't get my head around why. Why would we need to be here living these lives to learn lessons? To what possible end? Who decides what kind of life you should lead?
Let's say he's right. You come back as a chicken. How do chickens then progress up the reincarnation scale? Are there very virtuous chickens out there and, very naughty ones? Do they get demoted to earth worms? How do you be an exceptional earth worm? If it's a ladder, then presumably, we all started off as animals. Or, maybe we get a brief stint at being an animal if we sucked at being a human. No wonder so many people are turning vegetarian/vegan...
But anyhow, it seems ridiculous to me. You get punished in the next life for screwing up this one. So- in that next life, you already start off at a disadvantage presumably. Plus, you can't remember any of the mistakes you made in previous lives. In fact, you don't remember your previous lives at all. How is this progress? Imagine a child who is finding it difficult to learn how to write. They fail a test before they move into the next class. So- rather than help the child, the teacher further handicaps it by insisting it learn to write with its feet and toes. If you want a creature to learn and become better- which reincarnation is presumably about, why handicap it when it reincarnates and why let it forget everything it has already learnt? Maybe that is what happens but, it doesn't make any sense to me.
If you believe in reincarnation and presumably you think you've been given an unfair lot in life- what do you suppose you're being punished for? Do you see it as your fault? Whatever you did or didn't do in your previous life? Do you relate to whoever that person was? No- because you don't remember them. Your future self likely won't remember or blame you either.