Thank you for your Question.
A girl before marrying needs the permission of her Father or Grandfather. If she doesn’t have this permission, the Nikah is invalid! Hence in your case the Nikah would be invalid.
Kindly refer to the link below no. 2385:
My dear sister, at times, our love for someone can drive us to extreme ends, but it is only wise to seek shelter under the Shariah and that will save you from all mishaps!
Since you or your family don’t have a problem, and it is his side that has one, he should try and resolve this and send a decent proposal so that you become his wife.
On a side note, a man down not need to obtain permission of his father or grandfather like a woman does, hence he is very much capable to making his own decisions. (This does not mean I’m suggesting he goes against his parents, rather he should know his rights and maybe that will help solve his issue much easier).
I will recommend you to speak to your local Aalim who can intervene and play as an intermediary to resolve the issue.