Is it a fetus or is it a baby? It doesn't matter, it's so early that you can call it what you'd like. I think it's fine that they're looking for co-founders. They could just say "hiring first employee," but sounds like they're looking for a person who will be more involved than that.
If it dies, the law considers there there is a very large difference. :-)
More seriously: The English language says that "co-founders" are "people who found together"... not "people who found together plus anyone who joins them shortly thereafter".
Not necessarily. LinkedIn technically had 1 founder: Reid Hoffman. But really he couldn't build LinkedIn solo, after raising a small amount of capital (and using some of his own from paypal) he recruited 4 others to help him and become additional co-founders. So LinkedIn actually has 5 cofounders, but really started with 1.
What we need is another word that means "1st employee and oh so much more". I'm thinking "employee++", or "founder'" (that's founder prime, if it's not obvious).
In all honesty I think that all that is needed is a dose of reality.
If this to-be-hired person is going to be on-par with the existing "founders", in terms of pay, equity, and ability to vote to affect the outcome of the company, then I would call them a co-founder.
If instead this to-be-hired person is going to be a very senior employee with more equity than later employees, and some input on the product management stuff, then they are an employee, not a co-founder.
I do not know which case is true, my only point is that we do not need to invent new pseudo-titles for everyone to feel special.
