儲ける
もうける · moukeru · JLPT N2 · verb-ichidan
to earn
💰 儲 = 亻(person) + 諸(many things): a person who stores up many things earns
The kanji means to store up or stockpile, so the sense of gaining is the same. Stockpiling gains leads to earning money, and gaining a child is the same idea: adding a new member to the family.