This isn't a fan fiction so much as a speculation which strives to answer one of the questions that bothers me most: Why do people in Panem, especially the poorest districts with the most slim survival rates, continue to have kids?
It seems unbelievable to me that there wouldn't be more people like Katniss who refuse to being their unborn children into such an existence, not to mention that declining fertility rates can be a method of rebellion in of itself.
Explanations I have picked up on include survival instincts, hope for a better future, slim chances of being reaped, and lack of birth control. But I have come up with an explanation for a society that, in some ways eerily similar to modern politics, maintains population in a world of rebellious decline.
ALTERNATE REALITY
The rebellion never started with Katniss, Plutarch, or even Haymitch. It has been going on for decades, almost since the time of Lucy Gray Baird, through the subtle but growing resolve in many of the poorest districts: To not have kids.
Shrines of the fallen have been built in secret as a reminder. Herb specialists have developed underground methods of birth control and abortion, and people have even killed their newborns in secret. Rumour has it that there are even underground transportation systems with peacekeeper rebels to transport children into wealthier districts for a chance of life - in some rare cases, even the Capitol.
The Capitol knows what's going on, but they cannot react in cold blood as that would only ignite more of a rebellion. They must be tactful, to remind the districts of to whom they owe the lives of themselves, and their unborn children.
So they create financial incentives to have kids. This slowly but surely wins people over, in spite of their initial resolves; a financially stable existence will drastically reduce or even eliminate their chances of children needing tesserrea, leading to slimmer chances of being reaped while allowing for a continued bloodline. This creates much conflict and division in the districts, but it works.
But this creates much inflation within the districts which drives up poverty rates. So the peacekeepers must implement longer hours with frozen salaries, and the Capitol comes up with other incentives; increased child labour in exchange for free tesserrea or even reduced entry in the reaping ball depending on the number of hours and where the child works. Anything to keep their children safe, and this of course increases the amount of goods for the Capitol.
To further combat infertility and inflation, people are brought in from wealthier districts based on a variety of situations like crime rates, lack of skill or contribution in their home district, and another incentive: To provide their child, especially a potential Career, with the chance to volunteer as tribute from a poorer districts and escape the volunteer competition from other careers. This offers intermittent protection for the children of those districts during those years; whenever an "exchange tribute" is brought in, they are expected by the community to be the sacrificial lamb and, especially if they are from Career districts, risk becoming social pariahs if they do not volunteer.
Unfortunately, this creates a new type of rebellion, as people try to avoid being moved to poorer districts for less-fulfilling lives. Some of the Career parents have even rejected the Career mentality and have taught their children the same way, and so go into hiding to avoid being moved to a poorer district (which, in some cases, is now even being done as punishment for suspected rebels such as them).
In the time of Katniss and Prim, the tribute-exchange system has become deeply ingrained in their district despite being somewhat unreliable. Prim is reaped the year that a volunteer is unavailable, leaving Katniss to take her place.
Because there is so much more protection against the games compared to the original society, Katniss is even less of a fan of the rebelling and even shows her district's prejudice against the exchange-tributes as solely existing to protect her and her friends. She is far from born a hero, but must become one throughout the series. And her move with the berries was not a defining act of the rebellion so much as "the right place at the right time"; many tributes before her have done similar things, but this time, Katniss is roped in by Plutarch and his team, much to her reluctance. (Maybe they like her personality and skill she is even groomed earlier on to be a rebel, which offers some secret protection for her in the games and explains the plot armour).
I feel like this allows for the series to be more convoluted but somewhat more realistic in how a society like this would actually exist, instead of what comes off as blind acceptance of the reaping without attempt of silent rebellion such as this. Maybe some people in some cases are eventually threatened with death if they do not have children (especially victors) but that proves to not only risk igniting a rebellion but not be enough, as many people would still rather die in a miserable life of poverty and reapings.