Potty Training.

I think it also depends on the child itself. My baby is 6 months old but she doesn't sit down and poo since 2 months old. She wants to sit down to poo. Even in infant care, if the teachers put her lying down to poo, she will cry to be carried and placed in a sitting position to poo. Ideal for potty training can start from 18 months onwards or when the child can verbalise his/her needs. It is harder to potty train when the child is unable to verbalise. But each child has his/her own habits to poo, like some prefer to stand, some prefer to sit and even some prefers to lie down and poo. But I think your in law wants you to expose baby to sit down and poo. I do have friends whereby their baby is potty trained to poo only in potty by the time their baby is 7 or 8 months old. I think it is all up to the baby.