Australian citizen with UK passport and dependent visa

[call2bala]

Hello All

One of my friend who is an Australian but also got British passport through ancestors route many years ago but never visited more than 2 times in 2 decades. Now planning to migrate to UK with dependent partner & child.

I am not sure what route they have to start it. Could you please suggest best possible steps to follow.
Thanks

[CR001]

Spouse settlement visa.

https://www.gov.uk/uk-family-visa/partner-spouse

Was the child born AFTER your 'friend' became British???

[call2bala]

Yes child was born after getting British pas sport through ancestors route and marriage was done after getting british passport.
Thanks

[CR001]

Then child is automatically British by descent and can apply for a British passport directly.

Date of marriage is irrelevant.