Try this one...
The Plague Wars were brutal. From the starting attacks in 2078 to the collapse of anything resembling a state sometime around 2090 more than 97% of the world's people died. In the century since the withering of civilization, the population has only grown by about 33%. From about ten billion people in 2070 to 160 million people worldwide now. The Plagues no longer give even babies the sniffles but miscarriages, often so early that it isn't even noticed, are brutally common. People struggle to simply replace their numbers, infertility and sterility haunts the people.
The one note that might seem bright makes people bitter. A group of Parahumans is immune to the sterility. With the technological crash caused the Plague wars the reason for this immunity isn't understood or repeatable. These parahumans are a Homo Superior type. They are a handsome group, creative, high stats, extended lifespans, many advantages, and designed for a wealthy group of New England families. They are ethnically representative of "Old Money" families in 2050s New England. They are also culturally typical of New England as well. They are also rapidly increasing their numbers. Were normal families have two children if they are lucky, and three once in a blue moon, these parahumans have families of six to eight children. Because of their longevity, they can have their children over forty years with no problems. Meanwhile, ordinary human infertility, as medical infrastructure decays, is growing worse.
This seeming ray of hope causes bitterness and jealousy. Many groups feel they are being replaced and their cultures are dying. This wounds. As these families live only in the USA, charges of biological and racial imperialism are being launched.
Meanwhile, the remnants of the old technology and infrastructure continue to fade. This is a post-apocalyptic world struggling with poverty and decline. They need to increase the population or they'll be in the stone ages.
The PCs could be parahumans struggling to raise families and aid their communities in spite of the jealousy and bitterness directed at them. (Play up New England upper-class stereotypes. Sound like the
Howells, be as warm as
Jim Backus, as resolute and decent as
Katharine Hepburn, and a truly honorable and utterly stiffnecked New Englander. Study positive and negative New England stereotypes and play them to the hilt. Go a little overboard.)
The PCs could also be ordinary human government officials trying to prevent violence and oppression caused by jealousy and desperation.
A diplomatic campaign could be played as well. As these parahumans seem to be the demographic future of humanity, many nations would want a supply of parahuman babies to raise in their cultures and give them a future too. However, many people are competing for relatively few children put up for adoption.
Some governments might send agents to kidnap small children.
Remember, given the narrow ethnic base of the parahumans, many religious groups are staring extinction in the face. They'd want some of these children too.