長男, 次男, 長女 and 末っ子: which children are being ranked?
Read eldest and second sons within sons, eldest daughters within daughters, and 末っ子 across siblings. Family greetings, photographs and school plans do not supply a complete birth order.
長男 and 次男 rank sons
長男 (ちょうなん) means eldest son. In “長男が家族を代表して挨拶した。” (“The eldest son greeted everyone on behalf of the family.”), he greeted everyone on behalf of the family; in “彼らの長男は春から大学へ通う。” (“Their eldest son will begin attending university in the spring.”), the eldest son will begin university in spring. The representative role and future school attendance are separate details about the sons in these scenes.
次男 (じなん) means second son. “次男は兄と違って料理の道を選んだ。” (“Unlike his older brother, the second son chose a career in cooking.”) contrasts his chosen career with his older brother's, while “家族写真では次男が祖父の隣に座っている。” (“In the family photograph, the second son sits beside his grandfather.”) places him beside his grandfather in a photograph. Second son does not automatically mean second child when daughters are also counted.
長女 and 末っ子 use different groups
長女 (ちょうじょ) means eldest daughter. She is organizing photographs in “長女は家族の写真を整理している。” (“The eldest daughter is organizing the family photographs.”), and the eldest of three sisters gave a greeting in “三人姉妹の長女が代表して挨拶した。” (“The eldest of the three sisters gave the greeting on their behalf.”). Her rank among daughters does not establish her rank among all the children.
末っ子 (すえっこ) means the youngest child among siblings. “三人兄弟の末っ子は今年小学校に入る。” (“The youngest of three siblings will enter elementary school this year.”) describes the youngest of three siblings entering elementary school this year; “祖父は家族の末っ子を膝に乗せて話を聞かせた。” (“The grandfather sat the youngest child in the family on his lap and told a story.”) reports a grandfather sitting the youngest child on his lap and telling a story. The word does not itself specify the child's gender.
Separate rank from the scene's extra details
長男 and 次男 order sons, and 長女 orders daughters. 末っ子 identifies the youngest among the siblings as a whole. First identify the group within which each rank is being stated.
A family greeting or a seat beside a grandfather does not establish the birth order of other children. These examples also do not supply a fixed age gap or a complete ordering of every child in the family.
Does 次男 necessarily mean the second child when both sons and daughters are counted?
Show the answer and why
No. 次男 identifies the second son. 長女 ranks daughters, while 末っ子 identifies the youngest child among all the siblings. Keep each ranking with the group it uses.