Nigeria has people whose home language is English. I’ve worked with some. I doubt there are many Nigerians who only speak English and Nigerian English as spoken on the street can be as different from the British standard as Scots or Jamaican patois but there are plenty of native English speakers on Africa. This shouldn’t be that surprising. The Indian subcontinent has plenty of ruling class Brown Englishmen like the Bhuttos or Gandhis who are on their third or fourth generation of English language medium education. Anglophone Africa isn’t that different in that respect. The ruling class spoke English at independence and people from different language communities who have a common language in English will raise English speaking children.