NC for this - I've been reading here about step/ blended families and reflected what happened to me some years ago - I'm older now.
I grew up with step-dad from age seven to 12 - living in the same address. (I've never met my bio father). I was involved in step-dads family: spending time with step-cousins, visiting step-grandma regularly (she lived nearby) and so on.
Then one day when I was 12, I came home from school. Step-dad had packed his stuff and was leaving - this was last I spoke to him. I never got to say goodbye or anything to (step-)grandmother or cousins... My mum had his new partner coming in literally the next week after as well (I never got on well with him, he's no longer with her). AIBU to think this isn't normal way to finish step-families? We never talked with DM about all of this, we are not very close.