Several parts combine into one character.

兄 is a semantic compound: a mouth (口) drawn above a pair of legs (儿). The oracle bone shows the eldest sibling who teaches the younger ones with words — the "speaking elder." A meaning so literal it almost reads itself, and a character that pairs with 弟 (younger brother) to anchor the entire CJK kinship vocabulary.

Korean reading "hyeong." 兄弟 (hyeongje, brothers — also used in Christian Korean for "fellow believers"), 長兄 (jang-hyeong, eldest brother), 兄嫂 (hyeong-su, eldest brother's wife). The form 형님 survives as everyday Korean address — used not only between actual brothers but as a respectful between-friends term whenever the speaker is a male slightly younger than the addressee. Korean keeps the family-address use of 兄 alive far more strongly than Mandarin or Japanese.

Mandarin xiōng, 1st tone. 兄 (xiōng), 兄弟 (xiōngdi, brothers — when the second syllable softens to neutral tone, the word slides into "buddy / dude" register), 老兄 (lǎoxiōng, "old brother" = friendly address between men), 师兄 (shīxiōng, senior male classmate sharing the same teacher). The 师兄 / 师妹 system is central to Chinese martial-arts and university-lab kinship.

Japanese on-readings ケイ (kei) and キョウ (kyō) — 兄弟 (kyōdai, siblings — by far the most common reading), 義兄 (gikei, brother-in-law). Kun-reading あに (ani) — 兄 (ani, "my elder brother" — humble form when speaking to outsiders), 兄さん (niisan, "elder brother" — both a family address and a polite stranger-address for any young man on the street). Pop-culture Japan has built an entire emotional vocabulary around お兄ちゃん (oniichan, affectionate "big brother") that has spread worldwide through anime.

Memory aid: a mouth (口) above a pair of legs (儿) — the family member whose mouth speaks first.