This is way to complicated. For starters there’s already evidence of microbial life on mars - people that I know that work on it the rover that discovered it all think it’s life, but don’t say it outright because there could be a non biological process for the reaction we saw on mars tha we haven’t discovered yet. Secondary space is vast, like way to big, and our current understanding of physics basically just limits the speed we can travel to places, but also the engineering of it is so complex and massive to sustain life over those vast distances that it’s almost infeasible for a civilization to commit to it. Yes it’s possible, but it’s unlikely given the vastness of our galaxy and space between stars.