,cousins and family woes?

my cousin keeps sending me digusting text messages such as "would you be my ?" i try to tell his grandma but she thinks it's funny(he lives with her), show my dad and he calls him warning him not to continune(pardon my spelling) but his grandma calls and tells me off for getting my dad involved, so he comes back with more filthier messages witch i am not going to reapeat on this question but the words in it do contain a c at front and a t at end. i really need help. i'm sceard if i go to police this could break up my family as my aunt will tell some cottonball story turning my gran and other members of my family againt me. help.