From Page 4 of MN1 Application Form:-

Details of the child’s parents(If one or both are not the birthparents, please provide details of the biological parents on page14 of the form)

From page 32 of the GUIDE MN1

SECTION 6: CONSENT TO THE APPLICATION
For section 3(5) it is a legal requirement that both parents consent to the application.
(In the case of widowed, divorced or separated parents, this only applies to one parent.
If the child is illegitimate, only the mother needs to consent.)

The consent of both parents to the application is also a legal requirement for section
4D. Where one parent has died only the consent of the surviving parent is needed. The
Home Secretary may also waive this requirement in exceptional cases.

For other types of application we require the consent of all those with parental
responsibility for the child. If only one parent has consented, please explain why at
section 6.3. If it is not convenient for one of the parents to sign the form, consent can
be provided in a separate letter. If the father of an illegitimate child is making the
application, we would expect the mother to have consented.

Section 6.4 is to be completed if the application is being made by a guardian. Section
6.5 is to be completed by a child if he or she is making his or her own application.

If the application is being made by a guardian, we will expect to see evidence that that
person has parental responsibility for the child, such as a deed, will or court order. If
the child’s parents are living we would normally expect them to be British citizens and
settled in the United Kingdom.
You can't provide information that's no longer available or even needed.

Maybe you already read those sections, anyway hopefully it helps you