It'll be ugly and cause a lot of consternation within the family. Plus you'll never be the father to someone else's child that you would your own. Even though you think you could convince yourself to be. It's easy to avoid the disaster.
It's an easy call. Forego current pleasures for long term contentment. Don't make yourself look back and chastise yourself for not thinking it through.
Do what you will. It's your life to prosper or waste. You've been informed. And the world doesn't need more people who are confused and damaged because of a tumultuous upbringing.
This is the whole of the reason why it is preached that a man sins if he lies with another man's wife. Another man's kid undermines the family integrity and potential. How old is your neice?
Dude, citing the Bible as an authoritative reference is like saying The Cat in the Hat is authoritative! The only real difference between the two is that one had a single author, while the other had multiple writers involved.