Who is Mr. and Mrs Rees from Rees Howells: Intercessor and what is their importance?

Mr and Mrs Rees are Rees Howells' Aunt and Uncle who lived in Garnant. Rees' Aunt is headmistress of the country school. Rees' Uncle visits Rees just before the Howell's are to leave for Africa. When Mr. Rees learns the Howell's cannot take their son Samuel with them to Africa, he offers for Samuel to live with them. Samuel becomes like a son to Mr. and Mrs. Rees, and his name is changed to Samuel Rees