Honesty and loyalty are the backbone of any good relationship. Without this critical foundation, it's difficult to navigate through any tumultuous hardship if you can't even trust your partner's words to be honest and sincere.
Though one should always be transparent and trustworthy towards their partner, there's a point where withholding certain information could be a protective mechanism. There's absolutely necessary truths, and then there's unnecessary truths. If your mother cheated on your father and broke the family apart, it's perfectly reasonable to not want to share that information with your partner. There could be a lot of shame attached to those memories, and it's not like you were the one who cheated.
This brings us to the Reddit thread. In this story the original poster (OP) is a man who's revealed to his future brother-in-law the real reason behind the drama and hostility in their family – the mother's infidelity. But you'll have to read the full story below for all the juicy details.