Namechanged.
My step ds wants to permanently reside in the UK with us, he's 12. My DH (finally) took up British Citizenship 2 years ago. His mother is happy for him to live with us/ make his life here. She holds a passport from a non-EU country, as does step ds. Previously he has attended school here on a visa, whilst his father had a work visa, then indefinite leave to remain. I have British passport too, under the 10 year rule as I lived here as a main residence from birth until 11 years old.
Is there a way with can get DS a passport or leave to remain. His parents were not married at the time of birth.