I was in a similar situation once. Both of my co-founders needed to continue working their full-time jobs, leaving me to spend 70+ hours a week coding alone. We

I was in a similar situation once. Both of my co-founders needed to continue working their full-time jobs, leaving me to spend 70+ hours a week coding alone. We couldn't come to an agreement about what the equity distribution should be, so I left the company, and that was the end of things. Sadly, nobody wants to see 90% of their equity disappear overnight. They'd often rather keep 30% of nothing. You left out something important: What does Founder C think is fair? If you haven't yet, you should ask him his opinion, and get him to draw up a plan. Maybe it will be totally reasonable. I'd enumerate the potential ramifications, and use that as a rubric to score every potential solution that anyone suggests. You've got to consider A's feelings, B's feelings, C's feelings, your company's chances of success, your chances of raising money, etc. Come up with the rubric together, brainstorm solutions together, and score them together. Don't leave out C while you're discussing things. There are plenty of potential solutions. One is to buy C out of the company. He's contributed lots of time and funding so far, so he deserves compensation. Also, all three of you need to be on a vesting schedule. I believe the standard is 4 years to vest with a 1 year cliff. Chances are that a good investor will want to see that kind of arrangement, so maybe you should evaluate solutions with that constraint in mind. For example, maybe C can keep 30% but won't start vesting until he joins the company full-time. Or maybe he will vest 4x slower than the two of you until he joins full-time.