Non applying children

Greetings,

I am in the process of completing the family spouse visa and the application is asking about non applying children. My spouse, a British citizen, has 3 children (all British citizens) that reside mainly with their mother (my spouse's ex-wife). They are with my spouse on average 2 days per week.

The application is asking "Does Mr --- have any other children in the UK that are not applying on this application?" Given the two options of yes or no I have chosen "yes" as he does have children that are not applying on this application. However, I'm confused by the wording because the application at that point has only asked if I have any children that will be applying with me which I do not. So I do not understand why the question is worded as "does Mr --- have any other children in the UK the are not applying on this application" since nowhere did the application ask about his children prior to this.
The questions about just his first child seem endless and some do not make sense and I honestly do not feel they pertain to the application. Such as the application wanting me to provide optional evidence of MY access the children and my parental relationship to them...they are not my children.

The application also asks me to provide details of the role I take in the children's upbringing, including details of my parental responsibility or access arrangements. Again, they are not my children therefore I do not have any parental responsibility or access arrangements. It is my partner that has the responsibility and access arrangements...

Would it be unadvisable to answer "no" when it asks about if my spouse has any children in the UK that are not applying on the application and just address it in the cover letter?

Thank you in advance for your help!!

The wordings of the bulk of the application leaves a lot to be desired.
The correct thing is to answer Yes, provide the details you have and for the ones you don't have or can not get, address this in a cover letter to UKVI.
The forum is replete with members who faced same or similar and had successful outcomes to their applications.
More knowledgeable persons will give you further guidance as required.

I have exactly the same issue, really confused of how to proceed with it. My husband has 2 young children from a previous marriage and doesnt have birth certificates etc as they stay with his ex wife. It is confusing as hell. I currently have it checked as no as we have to complete our app by friday and currently I have wrote he pays maintence for two children in the next question and have explained the situation in the cover letter. I am really concerned about this question though as everything else in our application is fine i think.