also: おとむすこ
younger son
Refers specifically to a younger son, as opposed to an older son or a younger brother. Not a common everyday word; more often seen in literary or explanatory contexts.
He is the younger son among three brothers.
The younger son is still a student, while the older brother is already working.
長男 is the 'eldest son', the opposite of 弟息子 in birth order.
Standard kanji spelling.
Contracted reading; less common but attested.
Compound of 弟 (younger brother) and 息子 (son). The reading おとむすこ is a contraction of おとうとむすこ.