My cousin has a crush on me what should i do?

we have already made out and stuff. but he is not really my cousin he is my uncles son, my aunt stepson. but my aunt and uncle are cousins. so he is my cousin right? oh well everyone in the family says that me and him are going to end up like my aunt and uncle. he has my uncles name and i have my aunts name. nobody know that we have kicked it, but everyone was suspecting it even when it wasnt happening.