Pompejus is a member from the Netherlands. At the AH.com peerage system he is considered the Duke of Gueldres.
A Brother’s Betrayal - A 19th century Dutch TL.
The History of the Dutch Republic - A 17th century Dutch TL.
The character of Pompejus Snelheid from Snelheid, older brother to detective Nilsroy Snelheid, is partly based on Pompejus and serves as a Mycroft Holmes analogue within the show.