Um. Don’t you have the exact same problem even before the ‘can’t leave the whole farm to one person’ law? I mean, if SonA gets the whole farm, it can probably support him, his wife, and his kids. But what happens to SonB, SonC etc? Did they just starve? Never get to marry? Were there enough other available professions that they could all support themselves? Prior to that law, did they all join the army or become sailors or emigrate or what?
A good point, StarvingButStrong, and one I’ve wondered about myself. I think you’ve already given part of the answer. I don’t know how to check on it, but I suspect that a man without a farm or other means of support was a lot less likely to marry. That’s never totally stopped people from having kids, but may have kept down the numbers.
I’ve seen lots of references to second sons joining the military in places where male primogeniture was practiced (as under English common law). For Catholics the priesthood was another option.
With farms growing ever smaller and Catholics forbidden by law from buying new land,or leasing more than 31 years, Ireland became a land of tenant farmers, working land they did not own.
They might raise a cash crop on a part of the farm, just to pay their rent, but whatever they sold was likely to be exported, even during the worst years of the famine.
But note that the population in 2006 was only slightly larger than the population in 1851, even though deaths and emigrations were already beginning to cause a decrease in the population of the island. The population in 2022 is clearer lower than in 1841 and somewhat lower than in 1851. Again, a reasonable guess is that the population of the island will never be as high as it was just before the Great Famine began since, as in many countries, the population of the island isn’t increasing very fast.
The big change in how inheritance worked wasn’t really for Catholics. The traditional Irish inheritance model already divided the estate between the heirs evenly. What it changed was that Irish Protestants now inherited under primogeniture - everything goes to the eldest.
What changed for the Catholics was they were barred from buying land. Before, sure, you divided your land between your four sons, but if one of your sons was bad at farming, or wanted to go be a sailor, or died of typhus before having kids of his own, one of your other kids could buy the land from them, or buy land from the neighbors under similar circumstances, and it would still be possible for a Catholic land owner to have a sizeable estate.
Small farms are a lot more economically vulnerable than large farms, so they’re more likely to fail, and every time one fails, that land ends up being owned by a Protestant, because Catholics legally can’t buy it. This was deliberately designed to gradually turn land-owning Catholic families into peasants working on large, Protestant-owned estates, or workers in the factories in the urban centers. But when the Blight hit, it made every one of those small family farms fail all at once, and instead of the expected steady stream of impoverished Catholics looking for work on Protestant farms or in the factories, it was the entire Catholic population, all at once.