The PROKOSCH surname has a long history dating back to the 14th century.
While I am still trying to verify the connection to royalty or even a hint of a connection….
According to Godroms “Deutsches Namenlexikon” (German Name Lexicon), the name Prokosch also Proksch, Broksch, Prokop and Prokopf is from St Prokop the Patron Saint of ancient Bohemia, known to exist since the 14th century. It was a first name. The name is quite prolific in Vienna, Austria, and is recorded in early times as Procop Moelner 1447, Glatz, Procoff Funke 1532, Goerlitz, Silesia, Brocuff Rotbart 1505 Freystadt.
Other sources agree the name is derived from the first name “Prokop” or “Procopius”.
Prokosch – German Origin, Czech ending (Saint Prokop and osch).
German (of Slavic origin; compare Czech Prokoš): from a similar stem (Old Slavic proku) as the personal name Prokop. – Dictionary of American Family Names, Oxford University Press, ISBN 0-19-508137-4
The closest meaning to the PROKOSCH surname appears to be:
“The man who is carrying the sword at the head (sword foreman)”