Dear D.,
You are correct...you get the family when you marry your man. But, if he's your Mr. Right there are ways to get around the bad example set by his family members.
One possibility is to move to another state thus reducing the amount of time they would be spending with you.
Another is to teach your future children by example and break the cycle that your beloved's family has set. My family is the problem with us. It does help that most of them live in Alaska and we live in Oklahoma now.
Without going into too much details, I'll just say I was raised in an extremely disfunctional family who holds grudges for years. I chose to be the peace maker and to break the ugly cycle. I now have my own family...my husband of 23 years, a 29 year old daughter and 17 year old son. Add in three gorgeous grandchildren. My daughter and her family have an awesome relationship with my husband, son and I. In fact they will be moving in with us in June due to financial problems. My daughter and son were taught by example and when they questioned what one of my family members did, we explained, age appropriate of course, why it was wrong and what could have been done instead. We have used these incidents as learning moments.
We are not a perfect family by any means but we are NOT disfunctional.
I guess what I am saying is, if this man is your true love, marry him, but before you do, you and him need to make a pact to break the bad cycle that his family has developed. Make sure that HE is willing to join you in teaching your future children good habits and to have good attitudes. If he isn't willing to "let go" of his family and sides with them...then in my opinion you have your answer. Get out now. If he won't have your back now he won't have it in the future.
I have to quote the Dalai Lama here, "The basic thing is that everyone wants happiness, no one wants suffering. And happiness mainly comes from our own attitude, rather than from external factors. If your own mental attitude is correct, even if you remain in a hostile atmosphere, you feel happy."
The choice is yours, but by keeping a positive attitude the antics of his family will roll off your back like water on a duck's back.
I hope this has been helpful. Good luck and blessings.
W. Q