In an earlier thread, I already quoted from the intro. to the Broadview edition where the editor, Kathleen James-Cavan says that "primogeniture is a system that has no sensibility and makes no sense".

While the narrator makes it sound as though the Dashwoods' old uncle left Norland to John and his son on a whim because he had been charmed by a cute child, still it was probably inevitable that this would happen to to Norland.

However, with the mention of Mrs. Jennings 'ample jointure' at the start of Ch. 8, here we have the second woman in the story who has lost a husband and been left in charge of the family's money: Mrs. Jennings and Mrs. Ferrars. "The whole of Edward's fortune depended on the will of his mother."

It's interesting that the Dashwood ladies have been put into a situation that was probably quite common in their day, and yet proves not to be so inevitable as their old uncle's will made it seem.