The 1871 census of Ballaugh has William Brew, Hd, unm., 60, landowner, b.Ballaugh, with his niece and housekeeper Ann Brew unm aged 27 b.German, and his nephew (gt nephew?) William G Melbeau aged 3 b.Ballaugh.
I couldn't see him under this name in the IOM in 1881 or 1891.

The IGI has "William Brew Brew" bapt 22 May 1868 Ballaugh (illegitimate) son of Ann Brew. The actual parish register entry is unlikely to have any surname for him - the IGI adds the mother's surname for illegitimate children, even when both parents are given. So if the transcription is correct, she has given him Brew as a second forename, knowing he will be called by his father's surname in the IOM manner.

However the "G" is quite clear in the census scan, so a bit confusing.

Sue