also: おとうと
noun
younger brother-in-law
Refers specifically to a male in-law in a younger-brother position: one's spouse's younger brother, or one's younger sister's husband.
妻の弟、つまり私の義弟が週末に来る。
My wife's younger brother, that is, my brother-in-law, is coming this weekend.
妹の夫も私にとっては義弟だ。
My younger sister's husband is also my brother-in-law.
noun
younger stepbrother
Rare use for a younger stepbrother. In everyday speech, 義理の弟 is often clearer and more natural for this relationship.
父の再婚で義弟ができた。
After my father remarried, I got a younger stepbrother.
Attested special meaning-based reading; in ordinary text 義弟 is normally read ぎてい unless furigana or context indicates otherwise.
The older-brother counterpart: an older brother-in-law or, in some uses, an older stepbrother.
A more explicit and conversational way to say 'younger brother by marriage or family relationship,' especially useful when 義弟 might feel formal or ambiguous.
Means a younger brother in general, usually by blood or in a close family sense; it does not by itself specify an in-law or step relationship.
A compound of 義, here indicating a non-blood family relationship such as marriage or adoption, and 弟, 'younger brother.' The regular reading is Sino-Japanese ぎてい; おとうと is a special meaning-based reading noted.