What do you do? When your SO is kinda ugh about your mom and little sister because they get on his nerves and he doesn't…

What do you do?

When your SO is kinda ugh about your mom and little sister because they get on his nerves and he doesn't understand family cause he's never really know it. Then your mom can feel it because he's kinda rude to her and pick at every little thing your sister does. But then when you talk to him about it he always feels like your taking their side. I just don't know what to do!!!