When you're about four or five, a  flower will appear on your wrist, it's incredibly small, the flower cannot be picked off and will grow as you get older.

The flower is your soulmate's favorite color, your soulmate also has one that is your favorite color.

{It's the same flower, just a different color. Roses are the most popular while there are still some soulmate couples who have flowers that aren't roses}

One of the soulmates has it on their right wrist, while the other has it on their on the left.

When you make eye contact with your soulmate, it'll begin to glow faintly, a small roots will begin to grow around and up your arm.

When you kiss your soulmate, another flower will grow on the wrist you didn't have the original flower on, this time a separate mix of both of your favorite colors.

[Let me explain what I mean by separate mix
{I'm using Sanders Sides as an example}

Logan's favorite color is dark blue, Roman's favorite is red.

Their flower is a rose.

So when they kiss, the new flowers on their wrists won't be purple...
But instead look something like this.

Make sense?
I hope so. ]

When your soulmate dies, the flowers will begin to wilt, both the combined color flower and the single colored flower.

Once they both wilt...

You die as well.