When a compassionate ex-baseball star agrees to adopt the 10-year-old daughter of a former love who is dying, he soon learns that the young girl is actually his.

I like it, but I would switch the situation around (he's initially told she is his child, but after the mother dies, he realises the young girl isn't). It gives you a climax to build to, and a chance to play around with loving something that technically isn't "yours". It's a good idea to start with, but I would try putting a spin on it. I imagine he'd adopt her in the end anyway.

Good situation, but I'm not seeing much of an obstacle here. What's the flaw he has to overcome to build a good life for his daughter (after all, he's already 'compassionate')?