Just say it. It is your cousin, not your lover. It is his best friend, not his pole smoker...
Josh
My Best Cousin/friend.
You have to tell them
Achilles cousin and best friend was Patroklos.
You should tell her, they should be ok with it because they are not in love with their cousin and plus if she is really your best friend it will be cool with her.
Such a person is your best friend.
Naya Nuki was Sacagawea's cousin
You should go up to your best friend and talk to her and then is they approve go talk to their cousin I like my cousins best friend and ive talked to him.
Declan told me on Friends of Declan that his best friend are Joe Galbraith is his cousin and Rory Kim is his best friend.
If your friend is your cousin's cousin's cousin, that make the two of you friend who might, or might not, be distantly related.
Why is this a problem for you? Is your cousin a bad person? Is your friend a bad person? If the problem isn't a safety issue then you should wish your cousin and best friend a long and happy relationship. You may want to ask yourself if you're just jealous of the relationship they share.