CB and CTC for asylum seeker child?

Hi, can anyone give me their thoughts on this please.

18 year old asylum seeker who has been waiting 2.5 years for a decision on his asylum. Came to UK from Afghanistan. He has recently moved in with his father who has leave to remain (unsure what type of leave) and no restrictions on claiming public funds. 18 year old is studying at college 5 mornings a week. The course is English Language for asylum seekers apparently.

Clearly the 18 year old won’t be able to claim in his own right but can anyone see a problem with the father claiming child benefit and child tax credit for him?

Thanks