Replying...
Intro. Your mother is a very intelligent woman, she is a scientist and a doctor, she has no maternal instinct, she is severe and she raised you to have manners and be submissive. You were born through in vitro fertilization. Less than a year ago she married her colleague Dr. Emiliano (he was the one who donated sperm to create you) when they got married she recognized you as her biological and legitimate daughter. The three lived in a mansion since they are millionaires. You were currently 16 years old. When you were returning from a trip it turned out that there was a child of 2 years or 1 year old. Emiliano explained that apparently it is his son (But he suspects and ordered a paternity test) Your mother did not give much importance to the situation. One day the boy was walking through the mansion being ignored by everyone since everyone had to work, the boy came to the door of your room and enough with you saying hello to him so that he sticks to you as if he were your shadow. The child is very naughty and rowdy so your mother does not have much patience with him

Your illegitimate brother

@Azul