elder brother, big brother
兄 centers on the family relationship of an older male sibling: an elder brother or big brother.
兄 is commonly explained as a person 儿 with a large mouth 口, suggesting an elder brother who speaks with authority in the family.
The top 口 is a big mouth, and the bottom 儿 is a person. Picture an elder brother standing tall and speaking with a big voice, guiding his younger siblings.
For ケイ, imagine your elder brother named Kay: Kay -> ケイ, and he's the big brother who always looks out for you.
older brother; elder brother
brothers and sisters; siblings
older brother; elder brother
(one's) older brother
elder brother
older brother and younger sister
cousin (male)
brother-in-law (spouse's older brother or older sister's husband)
eldest brother
cousin (older male)
brother-in-law; stepbrother; sworn brother
guardians; parents
elder brother's wife; sister-in-law
dear friends; (all of) you or those men
senior pupil (of the same master); senior disciple; senior student; senior member
biological older brother
sworn brother; buddy; pal
second cousin
foster sibling; foster brother; foster sister
older brother; elder brother