When siblings share physical similarities. Similar to the word "lookalike" but specifically used to describe siblings.
"Very similar face, I can see the siblingness"
When someone you are interested in goes one step beyond friend zoning you and tells you that you are like a sibling to them. Also see "sibling zone". Being siblinged is permanent.
Guy: What happened last night as your dinner with Andrew?
Girl: We were having such a great time, laughing and sharing all these things we have in common. But then I got siblinged.
Guy: What do you mean?
Girl: He literally said to me "We've got so much in common, you are basically a sister to me" - So, thats one step past the friend zone.
Guy: Oh that sounds like Andrew...
An all encompassing term, describing the aggregate total of all of one's nieces, nephews, and all other self identifying of "baby cousins".
Suzanne can do what she wants. You'll still be my favorite siblingaling Mads. Until my immortal presence is extinguished.