Ask HN: Would you call guys who come in 6 months after, Co-founders?

You have an idea. And you originally start out with 2 other people. You build the site and it goes live. However, after less than 6 months, two of the 3 original founders (one being the developer) decide that the project is not for them. It's too hard and it's a lot of work.

You then find another developer. He's great. He's talented and he's motivated. He also introduces you to a new designer, which you soon bring on. The project is back to 3 people and everyone is working super hard.

Being a non-technical founder, but being the originator of the idea, and being the one who gave birth to it 6 months prior and watched it come to life that entire time, do the other two guys (developer and designer) deserve to be called Co-founders? (It's been 6 months since they've come on)

There are other factors, of course. And there's no question that their contributions are huge. And without them the company would not moving to the places it's moving today. However, given the idea, the 6 months prior, the investments both financially and in time, the name, the logo, etc, and most importantly the fundamental idea, should they be called co-founders?