hello. i allways wonder if cockroach and mantis both have 2 brains in their head and ass....  is it possible that they are like cousings, i mean, like cats and tigers, and also they have the same face... kinda

so my questions is ┬┐are they relatives, how close are each other, can u explain why they look similar.. kinda...?

No, neither cockroaches or mantids have two brains.

Both groups (the Mantidae and the Blattodea) belong to the superorder Dictyoptera, so they are more related to each other than any is to any other group: http://en.wikipedia.org/wiki/Mantis. As such, they will share a number of characteristics (that could be physical or genetic) that group them into the superorder Dictyoptera that excludes other groups of insects...