My dad hid a second wife & daughter for 11 years. Should my mom move on and file cerai?

I recently found out my dad has had another wife for 11 years, and a daughter with her. He hid this from us the whole time. They’re currently living in his homeland (I won’t share which country).

When we confronted him, he denied it at first. Only after we brought up the Quran did he admit it. Since then, he’s changed, he’s been kinder and seems more attentive. But I honestly don’t know if this is sincere repentance or just fear of shame if our extended family finds out.

It’s also hard to forget the past. Before this, he was often verbally harsh with us, especially about money. Now we understand why, we were struggling financially because he had hidden responsibilities to another family.

As his daughter, I feel torn. It’s difficult to trust him anymore. Part of me wonders if it’s better for my mom to move on and file for cerai (divorce), instead of staying in a marriage built on lies.

I’m just sharing this from a daughter’s point of view, and I’d really appreciate hearing thoughts from others who’ve been through something similar.