Is it wrong to dat my family member???? PLZ HELPP ME!?

okk, well i like my 3rd cousin on my moms side..and i dont think it matters but i really love him and he loves me..we have soo much fun with each other and everything but none of my family memebers know except my loving sister that i trust!! soo were dating but know one really knows..wat should ii doo?? PLZ help..i need some advice..