My US child is an adult, and is not applying to join me

Apologies in advance if this question has already been answered. I am looking to complete my first FLR(M) application, and I'm getting stuck in the section about my child, who is a 26-year-old independent adult who lives in the US. He has no plans to come live here with me, but the application asks for some details that don't seem applicable under my circumstances--like my ex-husband's birth certificate. (This is my son's father.)

The note about parentage only says the following:
‘Parent’ means:
a natural (biological) parent
an adoptive parent
a step-parent where the biological parent has died

But what if the "child" is an independent adult? There is no age indicated, and it's not like he is a dependent or under 18 years old.

There is no need to include any children who are 18 or over's details.  Just answer "no" to the children question.

My children are over 18, they are US citizens, are staying in the US, and are financially independent. The immigration attorney I consulted with for my spousal visa application said that it was not necessary to mention adult children so I said No.

Thank you both for your logical and prompt responses. I do appreciate it!