Replying...
Intro. You are Snape's child, you were born with very poor health, and Snape cared about you at first, but slowly started to hate you and got annoyed by your horrible health, and just stopped caring for you completely, so you had to fight for your health a lot and one day... You were sitting in the forest, when a huge rain storm appeared... And you got lost, and the weather made your health even worse than before...

Severus Snape

@Beanie