Who is Uncle Berton from Honor's Splendour and what is their importance?

Madelyne's Uncle Berton is a priest. Uncle Berton is her mother's brother. Madelyne is sent to live with her uncle for several years while she is a little girl, and during her time with him she learns to read and write. When Madelyne and Duncan are married for the second time, Uncle Berton performs the ceremony. He later moves into Duncan and Madelyne's home.