Is it normal for my bf to be obsessed with my ex's penis size?

This is getting annoying. He started dropping little joke questions about how big my ex was, and then they became serious questions. I just kept saying 'o your fine honey' or tell him he's bigger than my ex b/c that's what he wants to hear, but he badgered the truth out of me. So I just said yeah it was bigger than yours, but I didn't even have sex with him, nor do I want to even see the guy again. Now when we have sex, he'll ask me afterwards sometimes if I wish his penis was as big as my ex's. This is just weird. I tell him the truth there too and just say, No I love yours, you're really good. ... And it seems like he doesn't believe me. I don't understand why he compares himself to someone I don't like and never slept with, and honestly if it weren't for him bringing it up I'd forget about my ex & his penis altogether.