Oops, it doesn't look like 'sibling and girlfriend day' is a national day..

Other days

lisp

Lisp Day
prosecco

Prosecco Day
tulip

Tulip Day
emoji

Emoji Day
bow tie

Bow Tie Day
nae nae

Nae Nae Day
ormille

Ormille Day
boy friend

Boy Friend Day
cuddle up

Cuddle Up Day
gum

Gum Day