Not such word in italian, nor in french. Us, latin people just say "fratello e sorella" "frère et soeur" while english and german have "sibling" "geschwister". Non-native english speakers, do you have a word for that? Does it miss ? I never had such a thought since today...
You can, but strictly it means brothers and if they are all female you should say "irmãs" instead. A similar masculine-but-covering-both-genders usage is typical in Slavonic languages too. Usually not in words like brother, but could be used in words like brotherhood (братство). Nevertheless a corresponding feminine noun usually exists, so it's not really a gender neural usage.
Also in Czech we have a perfect equivalent of siblings - sourozenci, and it's also neutral word (doesn't matter if they are only boys or only girls or mixed).
EDIT: Now I am not sure. I found we also have a word sourozenkyně when it's only about girls :-D
But anyway, sourozenec means "a sibling" and not "a brother" or something else. Although we tend to distinguish gender.
We are siblings = Siamo (We are) Fratelli (siblings; yes it can also mean brothers.)
We are brother and sister = Siamo (we are) Fratello (brother) E (and) Sorella (Sister).
Now if youre a girl and you have two other sisters and wanna say "We arw siblings" it would be..
Siamo Sorelle (Sisters).