When English and Indonesian talk about siblings

English puts more emphasis on gender, having brother and sister but no specific word to indicate their positions with regard to the speaker's age. You ought to add the adjective elder or younger, which is sometimes impractical.

Bahasa Indonesia, on the other hand, values more seniority as shown in kakak and adik. Both words are applicable to either a brother and a sister, depending on their age compared to yours. Kakak means elder sibling, adik younger sibling.

Only when one is to address their elder siblings (kakak) do they adopt different gender words according to their ethnicity or, more commonly, the addressees' ethnicity, e.g. (elder brother v elder sister) mas and mbak in Javanese, abang and mpok in Betawi, akang and tétéh in Sundanese, koko and cece in Chinese Hakka, etc. But in Bahasa Indonesia such differentiation doesn't exist; only kakak means elder sibling.

This difference isn't exclusive, though. Other languages have similar features.