This is a wild situation you put yourself in. True story. My dad married a widow with 5 kids. Then they had me. Her husband had died of cancer. So Thanks Dad. My mom was an exceptional woman. She was a main character type of person. All I can say is your girlfriend better be an amazing woman. My mom sure was. On the other hand, on paper this is a looser decision for a man. If you were my son I would tell you to really think about this because the risk/reward is really stacked against you. The best answer I can give is the heart wants what it wants. As far as explaining anything to anyone, your a grown man and answer to no one so fuck ‘em. Do what makes you happy. Will another man’s 5 kids make you happy? What’s her backstory? 5 different kids from 5 different men or what? How did she become a single mom of 5? What’s the baby daddy situation? I think context matters too.