Question: What do Constantine Maroulis and Janet Gardner have in common?

Context paragraphs:
Janet Gardner: Janet Patricia Gardner (born March 17, 1962 in Juneau, Alaska) is an American rock singer.  She is best-known as the lead singer and rhythm guitarist of the all-woman hard rock band Vixen.

Robert Marks (vocal coach): Robert “Bob” Marks is an American vocal coach, music arranger, accompanist, conductor, and music director located in New York City.  His students have included Natalie Portman, Britney Spears, Ariana Grande, Lea Michele, Laura Bell Bundy, Kerry Butler, Nikki M. James, Constantine Maroulis, Sarah Jessica Parker, Debbie Gibson, and Ashley Tisdale.

David Homyk: David Homyk (born in Canada) is an American singer-songwriter and record producer.  His music can be described as a blend of Maroon 5 and James Blunt.  A producer by trade, David has made recordings for many well-known artists, including Beyoncé Knowles and her sister Solange.  He tours and performs regularly, having shared stages with artists ranging from "American Idol's" Constantine Maroulis to the hip-hop legend & Hall of Fame inductee, Doug E. Fresh.  David’s debut album is called "True Story." .  On June 27, 2013 AOL hired David as its first live anchor.  He was given the job upon singing the morning news.

Pray for the Soul of Betty: Pray for the Soul of Betty (often known by the acronym, "PFTSOB") was a hard rock band from New York City.  The band consisted of Michael Hamboussi (drums), João Joya (guitar), Taylor, C.R. (bass) and lead vocalist Constantine Maroulis.  On March 20, 2006, Maroulis announced his departure on the band's official message board, and on May 13, 2006, drummer Hamboussi posted in his MySpace blog that PFTSOB had officially disbanded.

Fidelity Is the Enemy: Fidelity is the Enemy is a 2001 studio album by pop singer-songwriter Jim Boggia.  A track from the album, "Several Thousand" was featured in the ABC television show Men in Trees.  The song was also recorded by American Idol contestant Constantine Maroulis for his debut album.

Constantine (album): Constantine is the solo debut album of rock singer Constantine Maroulis.  It debuted at number 75 on the Billboard 200, selling around 9,000 copies in its first week.

Constantine Maroulis: Constantine James Maroulis ( ; born September 17, 1975) is a Greek-American actor and rock singer from Wyckoff, New Jersey.  He was the sixth-place finalist on the fourth season of the reality television series "American Idol", and received a nomination for the Tony Award for Best Performance by a Leading Actor in a Musical for his role in "Rock of Ages".  He starred in the title role in "Jekyll and Hyde" on Broadway, for which he received a Drama League Award Nomination for a Distinguished Performance Award.

I Think I Love You: "I Think I Love You" is a song composed by songwriter Tony Romeo in 1970.  It was released as the debut single by The Partridge Family pop group, featuring David Cassidy on lead vocals and Shirley Jones on background vocals.  The Partridge Family version was a number-one hit on the "Billboard" Hot 100 in November 1970.  The alternative rock band Voice of the Beehive scored a hit cover version of their own in 1991.  There have also been many other cover versions of this song, most notably, Perry Como, Kaci, Katie Cassidy, Paul Westerberg, Constantine Maroulis, and the new "In Search of the Partridge Family" cast on VH1.

Janet G. Mullins Grissom: Janet Gardner Mullins Grissom (born 1949) is a United States lobbyist who formerly worked in the United States Department of State and in the White House under George H. W. Bush.

Athan Maroulis: Athanasios Demetrios Maroulis (born September 22, 1964) is an actor, vocalist and record producer born in Brooklyn, New York.  He is the older brother of singer Constantine Maroulis and also has a sister, Anastasia.

Supporting paragraphs: Constantine Maroulis Janet Gardner
Answer: rock singer