[MRM]

I agree with the comments suggesting you present the issue in a different way than asking him to give it to you. My suggestion is to tell him that you've picked up playing a little and wondered if he would mind if you fixed up his old guitar and played with it for a while. I'd make the point that now that you've progressed from a beginner's guitar that you treasure the idea of really learning how to play on his guitar, a guitar that you and he both have a connection to and that might be an area of common ground to you as adults.