I've secretly had feelings for my cousin for years.
What do you like about your cousin?
I think that my cousin is hot and cute.
Attraction is not something that can be helped but you should stop yourself from being with somebody that is related to you. Apart from incest being bad, it is not good date somebody that if things go wrong you will still have to see.
Who said I'm going to date her? It's a crush.
It seems like you don't have any intention on acting on this crush, so it's not that big of a deal. It is strange to have incestuous thoughts, but it's good that you know better than to act on them. If you feel like these thoughts are intrusive, you may want to talk to a mental health professional.