noun
Refers to a child taken in and raised by someone other than the biological parents, whether through formal adoption or fostering.
彼らはもらい子を家族として迎え入れた。
They welcomed an adopted child into their family.
もらい子として育ったが、とても幸せだった。
I grew up as a foster child, but I was very happy.
Compound of もらい (receiving, from もらう) and 子 (child). The exact historical derivation is uncertain, but the word literally means 'received child'.