I'm sorry to hear that but similar things happen with alcohol, people drive drunk with their kids in the car and get into accidents, one mother was so drunk in Missouri someone came into the house and kidnapped her kid, the people are to blame, not the substance.
Of course it's the people! That's what the problem is. Too many people who want to get high. My step granddaughter is a slut anyway. Her daughter wasn't killed, but her leg was crushed. The slut refused medical care because with a disabled child her welfare would increase. More welfare, more pot.
Your step grand daughter should marry my brother, they sound like they are perfect for each other.
She has four children by four different men and has no idea who the fathers of any of them are. She might not marry your brother, but she'd be glad to have his baby.