We did adopt ours - they are my husbands sisters children and we inherited them when she died a few years ago. They were teenagers by then and, of course, we'd known them practically their entire lives. It's been a tough road - especially as we didn't want children.
I felt resentful for a while - still do sometimes - and angry. So angry with their mother for being a fuck up and then dying and leaving us to look after them. The kids too had a lot of anger, grief and confusion. They knew us as the cool aunt and uncle, but suddenly we were parental figures and were telling them off for not doing homework.
To cut a long story short, it took a lot of individual and family therapy to get past those initial feelings. And time. And love and faking the love when we didn't feel it.
We've now, at their request, formally adopted them and we're happy with our choices and love them and can't imagine life without them.....
But it was a long journey and even now, I can't help thinking sometimes that I didn't want this. I didn't want to be a parent - they call us mum and dad now which is both heartbreakingly wonderful but also claustrophobic.
We'll muddle through, the four of us, and hopefully we won't fuck them up too much....