You mention that he has taken to the mentor/mentee relationship, and have said elsewhere that he lacks skills or knowledge of things like SSH.
Are they actually learning and making progress? Or are they unwilling to learn and actually holding you back? If they are learning and developing, why can't you treat them as a very junior developer, help them develop their skills, and eventually they will become a useful asset to your team. You can maybe even sit them down and talk this through with them, I'm sure they have probably realised that their skills could do with improvement. It would likely turn out much better than going behind their back and trying to persuade the other co-founders to fire them.
They must have skills of some kind if they got the product to a point where they could raise money and hire others in the first place?
As for the equity issue, even if they do get fired, that doesn't mean their equity is up for grabs to award to new engineers. So it probably won't solve your issue their.
Are they actually learning and making progress? Or are they unwilling to learn and actually holding you back? If they are learning and developing, why can't you treat them as a very junior developer, help them develop their skills, and eventually they will become a useful asset to your team. You can maybe even sit them down and talk this through with them, I'm sure they have probably realised that their skills could do with improvement. It would likely turn out much better than going behind their back and trying to persuade the other co-founders to fire them.
They must have skills of some kind if they got the product to a point where they could raise money and hire others in the first place?
As for the equity issue, even if they do get fired, that doesn't mean their equity is up for grabs to award to new engineers. So it probably won't solve your issue their.