Do abusive family relationships continue throughout our lives, and how do we stand up to abusers as adults?

It seems that as the middle child, I was always the scapegoat growing up. As an adult, I became invisible or "the troublemaker," especially where my older sister was concerned. When I married my husband (I was married for 18 years but have now been divorced for 2 years), no one in my family (four siblings--three brothers and a sister) ever came to my two stepdaughters' events, including birthday parties, graduations, and even bridal showers and weddings. My mother made the excuse that they "haven't always been a part of the family" and they're "rude" because as teenagers they didn't know how to fit in with my family. My mother each year for Mother's Day gave plants and cards to each of my sisters-in-law (my brothers' wives) but never once acknowledged my husband on Father's Day. She told me to my face that she didn't like him; that he was "spoiled." Now that I'm divorced from this good man (who is still my friend and a wonderful person), I've been dating another good man for a year and a half. We intend to be married. Yes, we have problems, but we're working them out. I'm throwing him a surprise 50th birthday party this weekend. No one in my family is coming. Again, my sister, who claims to love me "more than anything in the world," is too busy getting ready to fly to Texas with my mother next week for my niece's graduation party, and the night of the party is her girlfriend's husband's birthday, so she's going over there. That's more important than my fiance's surprise 50th birthday party? He comes to all of our family events and has gone to my mother's condo and done work for her when she's needed it. I'm the last one my mother calls when no one else is around and she needs a ride to a dr. appointment or needs something picked up from the store, and then she's all sweet to me. My brother and his wife are "too busy with the kids' schedules to come to the surprise party." What's up? I've never once forgotten their kids' birthdays, taken their three kids to the Nutcracker ballet, the circus, events that I've spent a ton of money on with them and had a ton of fun with them. My birthday is never remembered by them, not to mention the fact that this sister-in-law had the nerve to tell me that I'm "expecting a lot from this family, so soon after being divorced," meaning that I shouldn't be dating another man. (She sends holiday cards to my ex-husband but not to me.) I'm furious. How should I handle this?