How old are these kittens?

I found these kittens outside and I'm going to foster them. Their first appointment will be Monday but in the meantime, I need to know how old they are. Because of their small size, I thought at first that they were about 4 weeks old. But now that I can see them up close I think they might be older and just small/underweight. But I'm not great at telling how old kittens are so I could be very wrong.

They both have what looks like full ears. I can tell they are both boys. They have their fang teeth. Neither of them have blue eyes. And they can eat wet food.

The black one (Pepper Jack) is spicy, so I don't have many pictures of him. The other baby is Colby.

Thanks!