Is there a way to ever forgive some if they cheated especially with a baby involved?

So my dumb twin brother cheated on his girlfriend he actually was about to propose to next month. They had a baby this year. When she called me she was crying and immediately packing at the same time since they live together and now she’s moving in a little with her parents. My brother is upset since she obviously took the baby with her (she’s not holding the baby against him) but I’m sure I mean not waking up to your child is hard. But he made his bed. She left while he was at work. Anyways they’re literally both being childish on social media right now sharing word memes.
Is there a way to ever fix this honestly? They seemed so happy like she was head over heels for him and he claims he loves her but you don’t cheat on people you love especially when they’re postpartum.
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Is there a way to ever forgive some if they cheated especially with a baby involved?
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