How are you eligable, and how long have you been a member?
I would make sure your in good graces first... at least 90 days of membership before letting him join. Have him call and join instead of doing it online. See if they do it without your access # first. They may just ask him how he is eligable and he can say he lives at your address and your a member and hes a family member.... see if that flies first.
Does he have proof he lives there with you - rent/lease contract? Drivers License changed to your address? etc...
They may ask for proof down the road
When you say add, do you mean as AU? If so then yes you can add him as AU (correct me if it's not about CC).
If he ever decides to apply for his own CC/loans and messes up, as long a you are not an AU to that account, it will not affect you.
My nephew was enlisted so I signed him up for NFCU (I paid the $50). I then signed my brother up on his son's account 2 minutes later ($50). Then I signed myself up using my brother's membership two minutes later ($50).
When the two ATM cards arrived at their house they went to a local CU and withdrew $40 from each card and let the accounts eventually be closed. Dumb move on their behalf. My brother's FICOs are all below 550 so financial knowledge is not his strong point. He didn't care that I was hooking him up, all he cared about was a one time small cash grab.
As for me, I have savings and checking with NFCU and a $22k Cash Rewards card in good standing. My membership account is now more than 4 years old.
I am a member for almost 3 years and have excellent credit
And asking about to add him as a member as a family member not about a authorize user
He doesn’t really have a proof of address besides three existing credit cards that he will be changing it to my address
As already mentioned, if you sponsor him as a 'household member' he should expect to have everything verified at some point, and he'll need to have every 'i' dotted and every 't' crossed. Seriously. At a minimum he'll need to have the correct address on his ID (matching yours) and to be safe a utility bill in his name. NFCU won't play.
The easiest route would be to help your grandparent become a member, then your grandparent could sponsor your cousin. If you have a grandparent who served then your cousin could use them as his sponsor instead of you (without your GP even having to join). You could also sponsor your mother/father who could then sponsor their sibling/your cousin's parent, which would make your cousin eligible without having to be concerned with locked accounts.
Just my 2¢.
He’s actually not my cousin he’s my nephew
In that case it could be even easier... simply sponsor his parent/your sibling, and then he would have a clear path.
If that's not possible, sponsor your parent, then they could sponsor him as their grandchild.
I would use the 'household member' as an absolute last resort, since when there's drama that's often the cause.