Need to let go

Ive been in a relationship for about 16 months now and btw i love this guy to bits..i mean hes never pushed me into anything i dont like at all..and i guess i am very luck to have him but the problem is that hes my sister-in-law cousins (i know its not something big) but to our family we're meant to have a cousins or brother thing relationships and if they find out they are going to be devastated now doubt. I really love him but i dont want anything to happen to him because i know if our parents do find out the first person they are going to shout and hit is him and then me. I dont want to sound heroic but i would need to sacrifice my love for my family and his own benefit...we have a long distance relationship so thought it would be easer as he could get involved with other people..mainly girls (which kills) and find someone who hes got better chances of exciding with..i really dont want to leave but im scared someone will happen to him...so far my friend understood our situation and left me some E-mails and offline messages so he would feel a little insecure but i dont think its worked because hes started to love me more..which is making it harder for me to let go..i really want him to forget me but i dont know how? what would actually help us?