I think that “infant” is legal language for a minor child.. not sure though”
Not sure about the legal term either, but I am pretty sure infant refers to just what it conjures up. And that is NOT a six year old. I believe that at that point you would refer to a child. I am guessing the term infant would be in the 1-2 year old category, maybe even less than 2.
I checked and indeed it is a legal term ( I thought I remembered that from a child and family law class I took)
n of INFANT
1
: a child in the first period of life
2
: a person who is not of full age : minor