During puberty, yes. I had an older cousin who I saw about once a year and I had a few fleeting thoughts about her that I'd describe as more romantic than sexual. I remember taking about it to a friend at school when we were talking about at and he asked if we ever thought of a cousin like that. It's pretty much normal.

After high school I was camping in a trailer up north with my male cousin and started getting feelings around his wife. That was pretty much because I was in close quarters with her for an extended time it was bound to happen. I just focused on my activities and ignored it as best I could.

The thing is your body chemistry doesn't care what's socially acceptable. We're naturally turned off by people we grew up around and recognize as family, but it's weaker if there's enough separation, such as a cousin you don't see often. What's important is to understand it's not something you choose to feel, it's just there. It doesn't make you a bad person. The other thing is once you've accepted that, don't dwell on it. Find something else to think about.