What are the Beauty Marks?
Ever Since the episode St. Olga's Reform School for Wayward Princesses I started seeing a big focus on the symbollic Beauty marks. We don't know the male gender can have them or what it means to one. Another thing we find out is the each symbol is a Suit. There are four basic symbols we use in playing card which are Hearts, Diamond, Club and Spades. So far each person has one of these beauty mark shapes on both of their cheeks. It is also hinted by Miss Heinous that only royal from Mewni have these marks
Who has the Suit Beauty Marks?
One thing we do know is that only female royalty of Mewni have symbollic beauty marks with a connection to magic are the female royalty from Mewni being Star and Queen Butterfly. Star Beauty Mark is Hearts and Queen Butterfly is Diamonds. Interesting enough if you were to look what color is represented for these there both red. The only missing ones is the blacks Suit Beauty Marks which are the Clubs and the Shades. If you watched the episode St. Olga's Reform School for Wayward Princesses, it is shown that Miss Heinous has the Clubs Beauty Marks when she broke her individually and her marks disappear when she tries to brainwash herself into being a "perfect lady". So we get another hint what causes this. I'm not gonna mentions how isn't from Mewni or Royal from what we know so far, but maybe this is hinting her origins.
What does this mean?
It means that every princess and queen of Mewni (I'm guess that possesses great magical ability)
has a Suit Beauty Mark on their cheeks and that there is at least one more princess or queen the will have the Shapes Beauty Mark.
P.S. Another guess is the everyone with the Hearts and Diamond beauty marks are good and the ones with the Clubs and Shapes Beauty Marks are evil. It would example why Miss Heinous is ashamed of her beauty marks.