I'm not. But if you reread the manga it comes up over and over again. Author probably trying to convey some theme about the beautiful but fleeting nature of life. So they compress the timescale to accentuate it by having characters fall in love and die young, but have kids who carry forward.
Maru, the freezing baby, and the hotel girl are all products of pairings between the first generation of kids, with their parents all being dead now. Probably some others I'm forgetting. It's not that I want it to happen, but at this point I'd be shocked if it didn't given the series' penchant for planting and payoff.