what visa for child born abroad

A friend asked the below question and thought would post here for contributions from board.

He is a moslem man married to a British and currently he has British passport. Two months before he naturalised he had a baby with his other wife in his home country. The child is currently 2 years and he brought the child to the UK on visitors visa. He wants to know how the child can have settled status.

Thanks for your contributions.

Other wife?

There are two major concerns here for me. 1. Did he marry the other wife before or after the British wife? 2. What is the other wife saying about her child being removed from her care?