When the parents said the sister now knew what it felt like, and what she put her through, she should have asked if they had a daughter she didn't know about, and that's who she caught him with when she came home from the hospital
They are like 6 and 5, and would only be able to interact with them at father's house. That means it would be impossible to keep a relationship with them without having to have one, that's extremely toxic at that, with the father.
I'm one of those people who had difficulty learning other languages in general because I have bad hearing (bad enough to keep me out of the military), so I know a handful of words in a couple of non English languages, and even then I doubt I'm pronouncing them correctly. Yet, if I were to marry someone who was from a non English country, and I mean ved there to be with their family, I would first explain about my hearing, then also try and learn more than how to order a coffee. I may not become even conversant, but would work hard enough that they would know I was making an attempt