Ask HN: Co-Founder is lacking leadership and self-management abilities

My two co-founders and me founded a B2B marketplace startup at the beginning of the year. I am the technical co-founder / product designer. Co-founder A, which is also CEO, has experience in software project management as well as managing and leading companies. Co-founder B had the idea, has lots of experience and expertise in the industry of our marketplace. Each of them is handling the sales effort of one side of the marketplace.

The problem we face right now is that co-founder B lacks self-management abilities such as: * setting goals * breaking down problems/goals into smaller parts * splitting his sales efforts into clear processes/stages * seeing problems as problems with the process and not just individual problems

At the same time he is an excellent at sales but his sales efforts also require some degree of change management, for which he lacks leadership abilities. He has many good product and he has already improved many of the mentioned skills since the beginning of the year. At the same time he also has ongoing personal problems, which are in no way his fault but still burden him.

We have no employees and plan to close our first round of funding at the beginning of the next year.

Co-founder A and I agree that B is essential to our company's success, due to his sales skill, product ideas and industry knowledge.

Co-founder A feels that co-founder B is not pulling his weight. He is putting in more than enough time, but lacks some skills. If co-founder B does not get better over the next few months, A's proposition is to get a fourth person on board, who gets some of B's shares and will support him.

While I understand A's standpoint I believe that finding somebody capable will take more time and effort than helping and coaching co-founder B. Co-founder A is extremely upset about the situation and wants to see co-founder B improve during the next months or else take action. I see the problem as very manageable.

What do I do?