You clearly made an account to write this, and you clearly know my posting history.
I am sorry this upsets you. I really am. It is a question even I struggle with sometimes. I've been raising kids since I was 13. And yet, I don't live with any. Not right now. I will again, very soon but you can't know that. My mom is in her sixties and we have an 11 year old, a fourteen year old we're trying very hard to keep out of jail, and a 17 year old who is really a fall down mess. Financially, emotionally, physically, mentally, they are mine. I pay, I council, I do the homework runs and the psych trips and the social worker visits and the emergency family counseling. Not all the time. But enough.
My mother in law just made the opposite case. They aren't mine. Live your life. Start fresh, don't tether yourself. But that's not an option. It was one of the first things I told my husband when I moved in with him: I've got three kids. Not all the time, I'm not raising them actively right at this particular moment, but I've got 'em all the same. And if you want to be with me, you better know that I am financially (etc. etc.) on the hook for their collective future and that's non-negotiable.
So which is it? Not quite a mom, enough of one? My parents will be close to seventy by the time the youngest is eighteen. She's mine. She will be mine. Long before my parents are dead, I'm going to be mom for all three.
So here's what really makes me a little crazy: you think because I am not the primary parent here, that I've never been put out? In the last month, just the last month, I've spent close to a thousand dollars, called the police, cased a bedroom, gotten beaten up, had my possessions stolen, spent all night holding a terrified kid, done a home reno, canceled SO MANY plans, took someone to the hospital, hid the kids from a convict/bio-dad, and kept everyone alive and out of jail. And I'm not talking about my relatively simple DINK life. I am talking in the thick of it with the kids. I do it over and over. This is not abnormal for my household, this is run of the mill. We're not dysfunctional, we've just got three trauma-ridden kids who need a LOT of help and I'm not there all the time, but I am there a lot. I'm not a sister because I was already an adult. I'm not a mom because I am not the full-time load bearer. I am something in-between and I don't know what to call it.
But I am broken. I am sorry that it bugs you that it is just in a different way than you.
So, yeah, I'd know absolutely nothing about having to "impose" on someone.