Do I have to provide my husband's son (20yrs old) name for FLR(M)?

[ykalbt]

Hello,

I am going to apply for my spouse visa extension soon in June.
My sponsor has got a son from the past relationship (Not married), the son is 20 years old and a British citizen.
I was wondering if his son applies to the question in section 4. The detail is below.

Regarding online form of FLR(M), in Section 4 'Dependent Children', and at 4.3,
" Does your sponsor have any children living in the UK whose parent is not you?"

Does his son apply to this question? My sponsor no longer has obligation to be a financial sponsor to his son anymore.

If the answer to 4.3 is Yes, does my sponsor have to submit any birth certificate of his son? His son has not responded to my sponsor for ages, also the mother of his son and my sponsor has had no contact for many years because of their relationship , therefore it is unable to provide any documents regarding this section 4, such as birth certificate or passport etc, even if needed.

I greatly appreciate if you reply to me at your earliest convenience indeed.
My visa expires at the beginning of June, therefore I have prepared the rest of documents I need for the application.

Thank you very much.