Interesting Lyn. And I'm really sorry for your situation, and hope it goes without too much heartbreak, although I suspect it's already too late for that.
I too married a man with a teenage daughter - 17 at the time -and we nearly broke up because of it.
I told him months into the relationship that if his daughter was going to come first in his life, then it wouldn't work for us.
I know we all talk about the cf life, and for me having a loving partner to share equally in life's ups and downs, was, and is, my main focus ( I enjoyed being single too, but in relation to the love thing, you know ? )
Anyhoo, He told me I came first, and always will, and to be fair it is true.
He loves his daughter, she's 32 now with 3 kids, but his main focus has been me, completely and utterly.
Don't get me wrong, even then it was difficult, as she used to look on him as an extended bank account, and as our incomes were the same, it used to rankle.
So I would put anyone off getting together with a partner with kids. Even if you're 110 % sure it's right, there will always be problems, and extended families can be the biggest source of unhappiness and heartache.