My now DH had "no cats and I don't want kids" on his online dating profile but he absolutely fell for my 2 cats once he had spent some time with them and within a very short space of time after meeting my 2 DC he backtracked hugely on the I don't want children thing. They were 2 and 4 when we met and both have SEN although DD has some disabilities too and was always very challenging.
7 years later DH says that it was obviously meant to be, and that he hadn't wanted kids because he was already a Dad, just hadn't met them yet! 2 years ago they chose to call him Dad and use Daddy for their biological father although they don't see him very much.
DH pooled finances as soon as possible so he could support us, was there for potty training, sickness bugs and all sorts of horrors before he was living with us, as well as parents evenings. He's never missed a sports day or school play. DD goes to him for every day day, friends falling out and other preteen drama. Now that DD is older she's developed a lot of anxiety and has verbal tics when she's stressed. I had taken the DCs to my in-laws (who incidentally are the best grandparents and I get on with better than my own parents!) and DD had not stopped ticking all day, it had been constant. She wanted to call DH and as soon as he picked up and said "hello sausage" she just relaxed, tics stopped and was chatting away for the next half an hour.
There are good men out there. Men who see being called Dad by a child, whether genetically theirs or not, an enormous privilege. Men who will bend over backwards for those children no matter what.
DH has admitted that he worries he would feel differently about a child we had together, and so asked that we don't have any together, so as not to jeopardise the relationship he has with his stepchildren. It was gnawing away at him as a what if and I was more than happy with that!
DS can't remember a time with DH wasn't in his life, and it's amazing how alike they are despite the lack of genetics. DS is determined to be just like him when he's older, and they have a shared love of mechanics. DH sometimes takes him into work on a Sat morning and they work on projects together. They are building a go kart at the moment.
I couldn't imagine anyone better to be a father to my DC. He's filled the void in their lives so completely. They are out there!