Bet you regret setting this game within an adrift space ship huh? How you gonna introduce new characters now? Where's my clone entourage with their only differences being hair styles and fashion?
You have to be a man and actually finish the game, start a new one. That's more than 99% of other WEG makers can do, so take pride that it's finally over. And I know you're not imaginative enough to come up with new positions other than oral/doggy/missionary/cowgirl.
I don't really remember what is explained in the beginning, been awhile since I replayed from start cause I always use my save.
But, if they didn't say that they were the only humans left for sure, then he could have MC's family detect another similar spaceship as their own, and then have that spaceship include a whole new family, if he wanted to introduce new characters.
Or he could get funky with it and try to see if he can make some sort of alien race models and stuff, who knows. Space is far bigger than earth, way more to explore and do.