On character development

So, I was walking down the road one day, thinking about my new novel idea and, in particular, one of the main characters. He's a man in his mid-30s, and he has a daughter who's about 7 or 8 when the book starts. He's a pretty likable guy, kind and sensitive, and definitely wants to protect his daughter, who's very important to him.
On that last thought, I stopped short, and exclaimed "Damn it!". It had just occurred to me that it requires two people in order to procreate.
Ordinarily, this wouldn't be an issue, as his loving wife would be waiting in the home. But due to the nature of the events of the novel(more on that later), he and his daughter have to be free to move around, without being tied down by another family member that needs to be consulted for any plot twists. This was a problem.

Immediately, I began trying out different scenarios. I came up with several, but shot down each of them:

Divorce - Child custody. Enough said.

Wife ran out - Seriously considered this one, but then realized that any woman who was enough of a bitch to run out and leave her kid would totally wreck this guy emotionally. He has emotional issues, but nothing like that.

Wife died - See above. He puts his whole heart into his relationships, and he couldn't handle someone who he loved like that just dying. Also, then I'd have to explain how she died, which is harder than it sounds. The second reason was actually more of a deterrent than the first.

Adoption - My friend had just picked this as a possible solution for her book problem, so I couldn't just steal the idea. Also, he doesn't seem the sort to go out of his way to start a family without having a wife.

Finally, it hit me. The solution was a bit of a play on the last one, adoption, but not quite. His brother and his wife died when the girl was still small, and he was listed as the person to take care of any children they might have if something happened to them. He was close to his brother, but not like he would be to a wife. So, while I can still explore the feelings of loss he has, I don't think they'll be overwhelming to write. I'm happy with my solution.

Now I just need to name him!