Advice

Cheyenne

So i have been talking to a guy for the past two days and we have a lot in common. And we have feelings for each other so i told my mom and it turns out he is my 5th cousin on my moms side. So my mom says no to us dating my dad didnt say anything and my grandmother my moms mom. Says its fine to date him because the genetics are basically gone by then. I need advice what should i do?