I am reading Harry Potter and the Deathly Hallows by J.K Rowling. In the last book of this series Harry, Ron, and Hermione are sent on a mission by Dumbledore in which they can't tell anyone what they are doing. On page 210 Lupin offers to go on the mission with them to help protect them, he says he doesn't want to know what the mission is (but of course if they want to tell him he will accept.) But in this book Lupin has also been married to Nymphadora Tonks which on page 212 we find out is going to have a baby. Harry yells at Lupin for trying to abandon his family when they need him. He says it is because he feels horrible for bringing another werewolf into the world.
Why I think Lupin would leave his child to be with and protect Harry is because he hasn't met his child yet. And to him Harry is like a son, I mean he taught him how to fight off dementors! He feels a connection to him, and he knows Harry cares for him. But with a new child he is afraid they will hate him for making them a werewolf and giving them such a hard life, and he doesn't want this. Lupin is scared to be brave, he doesn't want to put himself out there and be rejected.
Its like for everyone in the world. In their personal and professional (school/work) life. The feeling of rejection is horrible embarrassing and filled with regret. Whether its in school when you raise your hand with answer and the teacher says its wrong, or whether you ask someone out and they say no. This is just part of life and our minds stretch them out making them these horrible things. But really the teacher is glad you tried and the person you asked out is flattered. So Lupin's son or daughter will realize he is my father he loves me and I am his blood it doesn't matter. Or even the child won't be mad. Lupin is scared!