Just today my 2 year old drank shampoo because we haven't watched him (I was with his older brother). How do people even handle 4 kids? And how do you handle 2

Just today my 2 year old drank shampoo because we haven't watched him (I was with his older brother). How do people even handle 4 kids? And how do you handle 2 such that you think that having 4 would be great?