Obviously, your initial code base has some value to it.
The above framework nicely value the past/future contribution of each party to remove much ambiguity.
The best part of that document is the line "the founders who join the company full time and are committed to making it a success are much more valuable than founders who are going to sit on the sideline and be cheerleaders."
That said, if the three of you are equally committed, you should probably be equal owners, based on the information you've shared.
If I was the guy turning your idea into gold and you held significantly more equity than me just because you built a prototype, that fact would bubble up and bother me exactly when you don't want it to - when things get tough.
Obviously, your initial code base has some value to it. The above framework nicely value the past/future contribution of each party to remove much ambiguity.