Is there are word like "filial" that means the relationship between siblings?

The closest I can come is 'familial.'

http://www.thefreedictionary.com/familial

i don't find it gross or anything. i'm an only child, so i have no personal feeling of whatever towards a sibling. i can imagine that if i had a brother close to my age we could have done stuff together. maybe even with a sister? just not all the way with her! it's very bad to have a child between two siblings. it often causes serious problems. with half-siblings, less of an issue of course, and might be more like a direct cousin? i don't know. two cousins, as long as there isn't a generational habit of it, are much less likely to have deformed kids, but still a decent risk. two cousins can get married in many states. further away than a simple cousin just isn't a problem.

Relating to a brother: Fraternal,

Relating to a sister: Sororal,

I don t think that there is a gender independent word.

filial relationship