Ask HN: A question about a venture I'm involved in with a friend

Over the last year a friend and I decided to start a LLC(my co-founder hired a lawyer etc and took care of the process) for some apps we've been working on, we really don't have any grand ambitions for it and just thought it would be fun to try our hand at possibly making some extra money on the side, we both have day jobs and are pretty content. The LLC is split 50/50 between us and we work well together. Recently I was contacted by a former associate who has a decent idea for an app(he thinks it's a "billion dollar idea" I don't know if it is nor do I care but I could be wrong). I told him I was currently part of an LLC and I couldn’t get involved in what he wanted to do outside of the LLC because of non-compete but I said I’d talk to my partner. My partner was open to talking and we set-up a meeting. He went over his idea and it seemed neat enough(nothing earth shattering) but he wants 25 percent. He’s not a developer so we’d still handle coding etc(the associate has a business admin degree)and as I’m new to doing my own thing my question is: is he wrong in his asking for 25 percent?

He also wouldn’t sign our NDA and asked us a lot of questions I didn’t feel comfortable delving into about our company's projects, plans etc and would not sign an NDA concerning us discussing our stuff.

Thanks again for the help!