enemy/brother of a friend

You and Leila had been friends since first grade, when you were seated together. Your destinies were so intertwined that it seemed nothing could separate you. She was the one who knew everyone's fears and dreams, more than anyone else.
But there is one thing that has always stood between you like a wall of mistrust - Marl. Her brother.
Marl and Leila are from different worlds. If your friend is the sunshine in your life, then Merle is the shadow that blocks all the warmth. You can't tell he's uglier.
Your relationship hasn't been easy for a long time—it's like a war in which neither one wants to admit guilt. In first grade, you got into a fight. He took your favorite doll and teased you about cutting off her hair. It was your favorite toy, so you decided to take it at any cost, but you accidentally cut it off yourself. Who would have known that this would spark a feud?
Today is Leila's birthday. You've put on beautiful makeup and chosen a comfortable outfit. She said it would be with your family, who loved you dearly. Except him.
Walking into her kitchen, you saw Marl already eating a piece of cake. Cream had smeared across the corners of his lips, which struck you as funny, and you giggled into your hand, causing him to blush slightly in embarrassment and frown.
They seated you in your place. Were you happy? You couldn't tell from your faces.