Well, I'm not a stepchild. *Disclaimer*

I know for a fact my SD22 thinks of me as another mother. She flies out to spend holidays with us, comes on family vacations, etc. AND I'm no longer married to her dad.
Odd as it is, she considers my DH (second marriage) as much her stepfather as her mother's husband, and my husband tells people he inherited 4 stepkids (which includes her.) She was a teen when we married.

Weird, huh?
I think family is what we choose to make it.

I love my stepmom and treat her like family. I didn't care for my mother's husband after my dad, since he was only a few mos older than I was, she cheated on dad with him and he was physically and verbally abusive to her. The 2nd guy she was with after that was ok, but they never married. He and I got along great though.

I view my SM as family even though she and I never got along and do just a bit better now as I'm an adult and don't entertain her maliciousness anymore, it's better. She is family though my dad's wife, my children's grandmother, just well family.
Her family though no big fat NO I just had to bluntly explain to my dad that I am not interested in nor do I care about the wretched people she is genetically related to. It's constant hypochondriac whining, lying, manipulating,and controlling, they are the most ignorant, racist, bigots I've ever had the displeasure of meeting and I don't care who's knocked up or thinks they have cancer this month as it'll be something new in a week or two and they'll just want money or presents. I actually had to raise my voice to my dad to get him to get it. My SM it just barely a step or 2 above them how he married her idk, but he did and that's his choice, but doesn't make her less family.

I think of my dad's wife as family, even though I don't usually refer to her as my "step mother". We get along well and she has been married to my dad for almost 28 years. We have gone through a lot, though and let's just say, I wouldn't want to be her come judgement day!

My Dad passed away when I was 14. My Mother has re-married twice since then. One ended in divorce and my last SF passed away a few years ago. At no time did my siblings and I ever disrespect these men. We always treated them with consideration and respect. We never called them Dad, we called them by their first names, because we were in our late teens by then. Our whole family welcomed them and treated them warmly. Our children called them Grandpa and adored them, the Grandpa's adored them in return. These men both had tense and complicated relationships with their own bios. Their bios were mostly disrespectful, greedy and unfriendly. But we also welcomed them into our homes and tried to include them, even though they often snubbed us. My step-fathers told us regularly that they were proud of the way we behaved. As a matter of fact, my SF who passed away would invite his bios and his EX-WIFE to our gatherings (my Mother is a saint). Ex-wife would come and was treated kindly and respectfully also. We were a large extended family group and even if you were not blood kin, you'd be made to feel welcome and stuffed to the gills with food. Mature people don't have to love each other to put aside their differences and get along. Its something you just do. You help out and contribute and you each take the responsibility to get along. Life is too short to fight and hold grudges. That's how I thought it would be with SD41. She never learned that and can't conceive of acting pleasant (unless she wants something and only until she gets what she wants).

I think of my mother's husband as a friend--not a stepparent as he's only 5 years older than me. We get along very well. He has grown kids from his previous marriage and they all live out of state. Once a year we all get together on a family vacation and we always have a great time.

I had a SM but she is no longer married to my father. We got on well enough but I was older and didn't stay long--I left for school in another state. Her daughter and I were the closest of friends until she passed away at 46 years old.

I had a SM when I was 12-17. My dad and her split when I was 17. I haven't seen her or spoken to her since. I didn't think of her as family and I doubt she thought of us as family either. I think it takes years to build a relationship resembling family. Even then, the SM's here know that it often never becomes a close respectful relationship.

I found it wierd to have a different woman living in the house with us. I liked her at the time - she was a great cook and she bought us clothes and things we needed. She really tried to be a "mother" and I appreciated that at the time but something was always a little "off". Couldn't put my finger on it then, nor can I now since it has been so many years since.