Well then, you really need friends who believe you more.

Kiss him in front of them

Gross you shouldn't kiss your cousin.

Well yeah but... He is her boyfriend sooo it's obviously okay don't you think?

No because they think he is there cousin and if he went so at to convince of it he could also pretend to be disgusted by her kissing him

Then they think they are Lannisters!!!

I can't see where OP is from, but in some places, I doubt OP's friends would even care.

that's the point

Are you sure he actually said that? You didn't just imagine it?

*hug*
Wish the hug could be real, so imagine it instead :P
But seriously, ouch. Sorry OP, hope at the end of the day your bf fesses up.

Now is the time to just go along with it and say, "I thought I might as well keep it in the family," before giving him a kiss.

I'm surprised your friends didn't in turn claim to be your other cousins that you paid to pretend to be your friends.

Haha that would be hilarious!

Sounds like he has a nice sense of humor, but it is frustrating to try and prove something, only to be let down again. I hope your friends will believe you soon, it would be hard to fake a potential wedding!

Your boyfriend is awesome

I hope he fesses up I'd have gone in the huff but that's just me, I don't see the humour in this so...

Then you must be a pretty boring person. Lighten up.

It's not funny to be the butt of someone's joke though, or to feel like no one believes you. It's easy to see the joke when you're on the outside. Some people may be able to laugh it off but for others, who may have been the butt of people's jokes all their lives and been made to feel like no one takes their feelings seriously, then it's not something you can just shake off, and being told to 'lighten up' again just invalidates their feelings. I'd be upset if that happened to me too. I hope he apologises because even though it might be a joke to him, it's obviously upsetting for OP.

Well, I am some one who is always the butt of the joke, and you know what, I can fucking laugh it off and get over it, people are assholes, so don't pay their jokes any mind, laugh at yourself more than they laugh at you.

that sucks. but it's funny!