My mom's been married multiple times. I have two stepmoms, and four stepdads. The first stepdad adopted me (I call him my "growing up dad") and I didn't even know I wasn't 'his' until I was older. Never thought he 'hated' me. He remarried a woman who I sort of thought hated me-- short story, she had a lot of allergies and a lot of migraines and just had a hard time 'dealing' with us visiting in general. My bio dad's wife has been my saving grace in many ways-- I met her (them) when I was 14 and never thought she hated me. I've grown to love and appreciate her care and concern over the years.
As for the last three guys my mom has married-- well, she's got her problems and knows how to pick'em, so to speak. I don't think they were typical stepdads, I guess, because the one I did live with from 8-14 was categorically abusive. Her 4th husband was just a real jerk and I was 17 when they met, 21 when they married.
I would say that the hardest things to deal with regarding my stepmom and adoptive father was that we felt she didn't like us or want to be with us because she was so sick. We didn't understand that someone could be so beset by allergies, and our mother practiced a lot of parental alienation toward all of her exes and their spouses.
My advice, be the best mom you can be to all the kids, be present, and be patient. If you are loving and looking out for their best interest, they'll eventually see it. It took me some time to see how much my bio dad's wife stood up for me, stretched herself for me, and showed me that there were better ways to live. I love her for it so much now and we have a good relationship.
It's brave to be a good stepparent!