@zanahoria
I feel her discomfort when being forced into the strict gender boxes of the times
Ma often has to do 'mens work' when Pa is away, once ploughing all the land. Their only son died as a baby leaving four daughters, the eldest is blind, there seems to be a theme throughout that Pa often treats Laura like a son and teaches her things like fishing that are usually the domain of boys. I think Laura slowly realises that life is not always like that, even though she proves many times she is as capable as boy, her life will be different.
In one of the later books she meets a cousin and they ride horses across the prairie and talk about how they feel free at that moment but see many restrictions on their life. I think it is then that another cousin who married at 13 is mentioned.
Absolutely to the sons thing -- I mean, having children was partly an economic decision, balancing mouths to feed against extra bodies to labour, and one of the gambles was girls vs boys, of whom much more economically-productive farm labour could be expected.
It shows up again in in a different context in LM Montgomery's Anne of Green Gables where it's made quite explicit that the boy Marilla and Matthew intend to adopt is nothing at all like what we would consider modern adoption, but a purely economic decision -- they don't have children, they need extra hands to help with the farm work, therefore they want a strong boy, who will be treated like a sort of unwaged, live-in, permanent hired boy, but with the understanding that he will inherit the farm on their deaths.
One of the things that Anne's arrival makes clear is that, because the Cuthberts don't have lots of small children like the other families to whom Anne has been 'boarded out' from the orphanage, adopting her is both an uneconomic decision, and a completely different type of undertaking -- for one thing, she can't be put to sleep in the room off the kitchen that had intended for the boy they meant to adopt, which was definitely more rough and ready 'servant space', and as Marilla is well capable of all the housework and lighter outdoor work like the chickens, Anne is of no economic use (until much later, when Matthew has died, Marilla loses much of her sight, and ends up adopting the two young children of to a dead relative.)
On the Ingalls boys situation -- three generations of the Ingalls family either miscarried or had stillborn boys (Caroline, Laura and Rose), or had boy babies die in infancy. I seem to remember reading at some point various theories about rhesus negative blood, or guesswork connections to PCOS and diabetes (which Laura, Grace and Carrie all had, apparently).