Can investors tell if a founder relationship is eventually going to be a problem?
I think it’s pretty hard to tell — because there isn’t enough time typically to observe the dynamic properly during the typical diligence window on an investment.
As a prospective investor, you usually get enough time with the CEO to get a sense. A sense if she will go the distance. If she/he wants to build a unicorn. If she/he has enough presence and drive to build a great team. And also — a sense if there are issues. And a sense if they might be a sociopath, or have other similar issues.
But you typically don’t end up spending as much time with the other founders, and not enough time with them together to observe enough of the friction you’d see if you are in the trenches with them.
This is why to me vesting schedules are super important. They protect the more committed founders from the less committed ones. More on that here:
Founder friction is unfortunately very common. A founder quitting or otherwise moving on is common, as well. A founder moving on very early with all his stock, having done very little of the work? You’ll regret that for a long time.