A sibling is your brother or sister. The word sibling once meant anyone who is related to you, but now it's reserved for children of the same parent or parents. It is a word that was once out of use but then brought back into English in the early 1900s as a useful word in anthropology.
Is there only one answer to the question? If so, I would guess communicating. Although analyzing influences and setting goals could be correct as well.
