Mycroft Holmes
From Jenny Everywhere Wiki
In the Prime Universe, M. Holmes (PROSE: Wanted for Questioning) was the brother of Sherlock Holmes.
He one of the guests at the Christmas dinner organised in 1895 at 221B Baker Street by Doctor Watson. Also invited were Sexton Blake, Mrs Hudson, Inspector Lestrade and Jenny Everywhere. (PROSE: The Time of the Toymaker)
“M. Holmes” would later be included in a list of Jenny's “known associates” across her incarnations on a Wanted poster put out by a large conglomerate of security organisations. (PROSE: Wanted for Questioning)