Yeah not sure about all that - 2 years in space and you end up sterile at the end of the trip....I'm not sure how we will populate Mars that way? I guess we keep eggs and sperm in cryo till we get there maybe? or is the uterus knackered by space radiation too....I just don't know. Gone be a while if we have to incubate people in fake uteruses... given we haven't invented that yet.
Repopulation won't be done the conventional way, there are too many variables to contend with, manily, with the raising of kids and the flaws that some are born with. Thus the best way, would be cloning of selected person's which would be conducive to making a supieror race of inhabitatents. Conducive to life style on Mars.
If we orginally came from Mars, it was the smartest and strongest that cause the population to be what it is to day on Earth. Stands to reason that if we return to our previous planet, making sure only the smartest and strongest by cloning is the answer.