If anyone can offer advice, please help.

My boyfriend, who is in Nepal, is in the process of applying for student visa for a masters degree. He's been accepted to a good program but didn't receive any assistantship/scholarship. He's been told he can apply for it from his 2nd semester onwards. So, for visa application and I20 purposes, he needs to show that he has to show personal funding.

The scenario right now is that my brother, who is working at a prestigious firm in the US, and is a greencard holder, has offered to do the needful to process the sponsorship, stating that my boyfriend is his "cousin". My boyfriend and I are not engaged or married yet but plan to do so once he gets to the US since I am also here on OPT right now. Is this a good procedure to show sponsorship for the student visa? Please let me know what steps we will need to follow to process the sponsorship. Thank you.