One our best kitties ever was 7 weeks old when we adopted him from a shelter. Generally 6-8 weeks is considered a safe age for a kitten to be weaned.

I think it's great that you are taking them as a pair. Kitties are very social (contrary to popular myth). We have 4 and they all keep one-another company. 2 of our boys wrestle and play a lot. They are very entertaining.