I have only got Fawkes, my bezzy m8 the big spacker.

How many on the game can you recruit?

Can you only have 1 buddy at a time?

In fallout 3, 1 dog, and 1 non dog is the limit.

if you got the expansion packs, that broken steel one, you can kill dogmeat and recruit another. if you have the puppy perk, you can dogmeat again and recruit.

I've only been up to two, Fawkes and Cross (after Dogmeat died at the hands of a glowing one), and that was enough for me. If you have too many, your loading time gets really long.