EUSS family permit for parent's adopted son

[Jimmy2024]

Hello
I have "Settled status" in UK under EU settlement scheme and I am a citizen of Germany.

My mother is an Indian National and she will be applying for EUSS family permit as she is old and need care.

My mother have an adopted son in India who is 17 years old. Is it possible for my mother to add or apply for her 17 year old adopted son in her EUSS family permit application?

While she is filling EUSS family permit application it does ask for "financially dependent child under 21" and it it says that they (dependents) will need to apply separately if they want to be with her in UK.

Kindly guide me in in this regards how her dependent adopted son can apply for EUSS family permit or what are the options.
Thanks