@zvonac:
in my opinion, it wouldn't be very unprofessional to try and get closer to the guy… he is not your patient, his grandmother is, so I don't see a big problem here. Yes, you might end up without a job if he doesn't like you back, but overall, I wouldn't say it would be unprofessional on your part.
If you're doing work for someone's family then it seems appropriate to act professionally so long as you are working.
As well, if you're in a situation where someone is needing a nurse, there's probably plenty of intense emotions floating around and that just seems like a minefield not worth walking in. There's a remote chance it could go well, but personally I could imagine plenty more ways it could result in someone being absolutely disgusted.