Whittleisstressed · 13-15, F
As long as you feel uncomfortable about it, you need to speak up. He was violating your self-respect and dignity as a young child. Hence, it is right to talk to your parents about this.
Please tell them. I kept quiet about stuff my brother did to me as children and it's a major regret nowadays. No uncle should be inviting a child into his bed, much less alone.