Oops, it doesn't look like 'sibling aka sissy day' is a national day..

Other days

cuddle up

Cuddle Up Day
stud

Stud Day
girl friend

Girl Friend Day
nae nae

Nae Nae Day
tell a fairytale

Tell A Fairytale Day
ruby

Ruby Day
camera

Camera Day
tulip

Tulip Day
first love

First Love Day
fiancee

Fiancee Day