Is it normal to have a crush on a cousin?
Depends.It depends
A crush on a cousin can happen, and having the feeling doesn’t make you a bad person. Whether to act on it is a separate question, with family boundaries and possible complications to consider.
Feelings don’t always follow the neat rules you’d pick for them, and an unexpected crush can happen even within a family. You’re not weird or bad just for having the feeling.
Acting on it is a different matter. Family norms, how close you are, and the possible effects on the wider family all matter, so it’s okay to keep clear boundaries and let the crush pass rather than pursue it. If it’s taking up a lot of your attention, some distance can help.