British Expats - Form UKF referee problem

Hello my first post here thank you for having me.

My situation I am looking for advise on is as follows. I am British by birth. My son was born in Denmark in 1998 (mother Danish) but we were not married at his time of birth. Due to ill health of my son he came to live with me here in the UK in June of this year 2019. With Brexit now a certainty I am worried about his status as he has to live me becuase of his ill health and can not live with his mother who is in Denmark. Anyway on checking I think he is eligible for British citizenship through me. Reading through form UKF I get stuck on the need for 2 referees , as he has only be in the UK since December and they are asking for 2 people who have known him for 3 years or more. Which I can not provide. He has lots of family members here but of course they can not be used. And the professional people who know him (his medical health team ) have only known him since July of this year.

Is there anything to be done about this ? I have all his other documents required birth cert etc Danish Passport and so on. IM really stumped by this. Sorry if my question is a bit long winded but really confused as to what entitlement he has if any.

thank you very much for taking the time to read this

Dino