You should count all individuals that fall in the following categories

1. Biological Children: Your (you or your spouse) natural children regardless if they were born in wedlock. Children where either one one your is a biological parent should be included.

Special circumstance: if you had a biological child that was adopted by someone else, you should exclude them.

2. Legally Adopted Children: Children whom you or your spouse have legally adopted and have obtained legal custody for immigration purposes, provided the adoption took place before the child's 16th birthday (or 18th in certain cases).