1 child in addition to the partner – £22,400.
2 children in addition to the partner – £24,800.
The financial requirement does not apply to a child who:
Is a British citizen (including an adopted child who acquires British citizenship);
Is an EEA national (except where a non-EEA spouse or partner is being accompanied or joined by the EEA child of a former relationship who does not have a right to be admitted to the UK under the Immigration (EEA) Regulations 2006);
Is settled in the UK or who qualifies for indefinite leave to enter; or
Qualifies otherwise under Part 8 or Appendix Armed Forces of the Immigration Rules in a category to which the financial requirement does not apply.
Therefore, it depends if the child born in the UK is registered as British before you apply for FLR(M) as to what Financial Requirement applies.
See also,
Annex FM 1.7 (click).