If I was going to be completely honest...I would advise against it.
Whilst you may not be directly related, there is still some level of relation - remember, you are still, essentially, his auntie's sister. This remains the case, no matter how you look at it. You're more of a 'distant' relative than a 'close' relative...but you ARE a relative, nevertheless. And what would happen if you were to pursue this any further? What impact would it have with the rest of the family?
Have you spoken to any of your best friends about this situation?
I do apologise if I have caused any offence. But that is my honest answer.