Remember…"less important" is a value judgment. It originates in another and has absolutely nothing to do with you. If, however, you were taught that you were "less important" when you were growing up, it may have been internalized. If so, there may be a place in you that agrees. That is about you and we can do something about what is "ours." It may be a long and arduous task but we can heal the misinformation given us. Right here and WWU, right now is a good place to start.
It is so sad to hear about the rigid MIL who reigns supreme. She is, of course, the most insecure person on the planet and has nothing but her biological history to define her. No wonder she will fight to the death to defend it.
What besotted young man in going to be able to put his foot down and say, "Not in my house." He is sometimes so besotted that he doesn't even know it's his house. It sure looks like it has somehow become "Her House"…without much of a democratic process. Old alliances fade away when the present looms to such a degree. Besotted morphs into "Where do my mom and dad fit into all of this?" And often what follows that is a whimper…"Oops…just thought I'd ask…please don't stop being cuddly and sweet. I am really hooked on cuddly and sweet."
See? We are back to besotted. Sometimes it lasts a lifetime. Other times it fades into…"Yes, dear."
Look back to where we started. A young guy, inexperienced, full of hope and wonder…never for a second willing to even consider betraying the love and trust he feels toward his family of origin. Never.
There are endless variations of this saga. There is the stereotypical MIL who brings her DIL to her knees on contact and never lets her get up. And we know about the DIL who says she is now the big cheese and no MIL on either side dare whisper…"Why? What for?"
In each case and in all of the ones not described…someone took over and a reign of terror commenced. (Occasionally, oh, so lovingly.) In each case, whether war was openly declared or insidious, someone wasn't challenged and stopped. The consequences of even thinking about stopping her melted the options into a puddle of fear that became a lake and then an ocean.
We don't study Conflict Resolution 101. It's not a required course, it isn't even on the list of subjects offered. We just don't know how. And "they" count on that. There are endless "they(s)." Look around.