I’d say no, but only you know if the friction it would cause is worth the risk it creates.
I had a similar position, with my BiL. He asked me to act as guarantor for a loan to get him out of debt spiral issues – refinancing his debts was a sensible thing to do, but the issue being that he had a bad credit history meant he was looking at a loan with some ludicrous APR. Not quite payday loan rates but something like 30% apr. I refused, not wanting to be linked to his credit rating and have my unblemished record dragged down, and instead took out my own loan at 4.9%, which i then gifted to him and he pays back the instalments.
Except – he then **** up again (literally, he got a girl up the duff) and now has to pay almost a third of his salary out in CSA payments. As a result, he’s broke, and i haven’t seen a repayment from him for over a year now. He owes me close on £7K and i suspect I won’t see it again, from him at least (his Mum has promised I will, even if it’s when she pegs out and it comes out of the estate before what’s left is distributed). But there’s no denying the £250 per month instalments going out each month would be more handy than £7K at some point in the future.
Even now – my head says no way but if it was the case of doing it again compared to him being in the same shit but to some proper lender – well, he’s family isn’t he?