Based on a post of Tumblr. Fred arrives in heaven and finds out Prongs is Harry's father.

"I can't believe we forgot. We never forgot before." "We had other things to think about." James replied, but Sirius could tell he only said so to make him feel better. It felt like they had betrayed Remus, leaving him to himself like this. It felt like fifth year all over again, and that thought made Sirius' stomach turn.