There are many reasons why a male cat might carry a kitten. One reason could be that it's playing with the kitten. If the kitten has grown up with its parent cat since it was a kitten, the male cat will play with it. 
On the other hand, male cats may carry kittens in their beaks as a protective measure because they are afraid the kittens might be in danger. It can also be a form of training for the kittens. Therefore, it's not just female cats that carry kittens; male cats do it quite often as well.
Usually, the male cat and kittens are playing, or the male cat is protecting the kittens from harm or training them.
