Jon Young is known for being a writer for natural sciences. He advocates through his books the need to preserve the natural reservation and the endangered species.
Uli Jon Roth is most well known for his career as a guitarist and for inventing the Sky Guitar. He has been active in the music industry since the year 1968.
"Who" would be the correct answer. The phrase "who is a well-known singer" in this case is functioning as an appositive. As such, "who" would take the nominative case, just as it would if it were the subject of the sentence.
Famous and well known means the same thing.
Who is nominative case as in Who ate the biscuits? Whom is used in the accusative case when the person is the object of the sentence as in The man hit JBJ, whom he disliked. The correct version is 23a Jon Bon Jovi, who is a well-known singer and actor, also owns an arena football team. Jon Bon Jovi is the subject of the sentence and is in the nominative case so who is required.
A relatively well known young French matador.
Jon Erik Hexum was a young television actor who died in a movie-tv-set accident.
Jon Cryer is best known for starring in the films such as "Hot Shots!" and "Superman IV." Jon Cryer is also known for his role in the hit television series "Two and a Half Men."
Johnny_mcNuggetz">Johnny mcNuggetzScott Young
Well Jon and Kate met at the hotel pinic where Jon works and Kates friend work
Writing a bestseller at a very young age.
Scott Young, a well-known Canadian sportswriter.
Georgie Spence is a well known young event rider