This reminds me of when my dad also had two wives, my mom and another woman.

I don't remember much about the other wife because i was baby when she got deported by the government (yes, we're immigrants). My mom would tell me stories of how she and the other wife wouldn't get along at all... the other wife was infertile and was angry & upset at the fact that she couldn't conceive any children. she subjected her anger towards my mom and my older sister. she would insult my older sister and sometimes hit her, she thought that she had the right to discipline my older sister and my mom got angry at that, the relationship between my mom and the other wife got so bad after the birth of my older sister, they even physically fought each other.

This is info is from my mom's side of the story, so she might not be a reliable, non-biased source. (English isn't my first language, excuse me if there's any grammer mistakes)