[slowhand09]

Siblings IS the only combination, unless you are playing word games. You have a job, with benefits available. Go to HR, tell them you want the additional coverage for your children. Mention that one is your best friend's child. Or your daughters best friend. When concise wording matters, this choice will become important. Else it is like the collective "we lost favorite actor|humanatarian|humorist|etc person this year" stuff in clickbait headlines. The collective "we" is about manipulation of perception and feelings.

This is not to minimize the loss felt by the poster I replied to's friend-of-a-friend. Its about not misleading by choice of words. Isn't that a big part of the original post?