I've had this problem with my family. I own a brick & mortar business with my brother, and I am a developer. I built a side-project that he was part of and he f

I've had this problem with my family. I own a brick & mortar business with my brother, and I am a developer. I built a side-project that he was part of and he failed to do his part, and it is just sitting, stagnating at this point. He has more ideas he wants to pursue and I'm unwilling, due to his role in the first. But because I have an ongoing partnership in the b&m business, it's hard to be fully forthcoming about not wanting to work with him. My situation is different in that I'm not going ahead with the idea without him. Mostly I've just put off working with him again and he hasn't been too persistent about getting started on anything. Even still, if I were faced with the conversation of "why don't you want me to be a part of this?," I would tell him exactly why. He wasn't a good co-founder in the past, I don't expect he will be this time either, and I'm not prepared to risk another business on him. I would tell your "good friend" that you don't enjoy working with him, even though you like him, and that you won't be including him.