Was your relative asking for a percentage stake in the company or a percentage of the profits? In either case, what I would tell him is that his percentage will be in rough proportion to his overall contribution to the project. Lots of ideas are needed to design, create, market and sell an app. Why should his one idea be favored above the others? At best, one could weigh his idea in proportion to its usefulness toward the end-product. He thinks he contributed 50% to the end product but why that number? Why not 10%? In any case, I don't think he should be paid anything until you recoup your fixed development costs. What if the idea doesn't pan out? It seems to me that he wants the risk-free part of supplying the ideas but wants you to go through the trouble and expense of building it. Did he offer to pay you anything for the trouble? I think most people would love to spend their days just dreaming up ideas and getting paid for other people implementing them. Indeed, this is my big problem with software patents and patent trolls in particular.