When do infants recognize/miss one steady caregiver?

I'm writing a short fictional story set in a historical orphanage. I'm trying to figure out how I should have the orphanage organized (I'm not looking for how they were organized in real life, I'm making up my own for this story). Anyway, I was curious what age the kids would start to realize that there was not one steady caregiver. When would it be important for the people to be steady in their life for long periods. Like a newborn might not notice if they were taken care of by multiple people (I'm not saying they can't recognize, but that it doesn't bother/harm them to have multiple caregivers instead of one steady "mother" figure). What age do you think kids would need a steady person to maintain a sense of stability in their life?