(written from a Production point of view)
Seth Woodbury MacFarlane (born 26 October 1973; age 41) is the actor who played Rivers in two episodes of Star Trek: Enterprise; however, he is best known as the creator of the popular animated series Family Guy and American Dad! as well as his latest creation The Cleveland Show. In addition to his minor roles on Enterprise MacFarlane had a character named after him.
MacFarlane is a big Star Trek fan, and many references to it have appeared in Family Guy, from the redshirts of the original series, William Shatner shouting "Khan!" as Tevye in a production of Fiddler on the Roof, to Quark and Odo (voiced again by Rene Auberjonois) from Star Trek: Deep Space Nine appearing in Stewie Griffin: The Untold Story!. MacFarlane has even worked Trek references into Star Wars productions; in the episode "Something, Something, Something, Dark Side" (a Lucasfilm-sanctioned re-telling of The Empire Strikes Back), when he speaks to the bounty hunters assembled on the Star Destroyer's bridge, Darth Vader, in the form of Stewie (who had previously used a baseball bat to destroy a mailbox on an asteroid with the name Nimoy on it) mistakes the Trandoshan Bossk for a Gorn, while in "It's A Trap!" - a similar treatment of Return of the Jedi - despite a desperate plea from Lando Calrissian (Mort Goldman), the Enterprise-D crew (in TNG-style uniforms, and therefore unaware assistance later provided by Lando's ship during a pivotal engagement) politely declines to provide cover fire at Endor rather than interrupt their afternoon tea break. Michael Dorn and Patrick Stewart voiced their TNG characters in that scene.
In October 2011, MacFarlane mentioned to the Hollywood Reporter that he was eager to reboot the Star Trek series for television: "I'd love to see that franchise revived for television in the way that it was in the 1990s: very thoughtful, smartly written stories that transcend the science fiction audience. I don't know who would give me the keys to that car." 
Also in 2011, Seth appeared in the documentary, Trek Nation.
Among the other Trek alumni who have lent their voices to his shows are Jonathan Frakes, Alexander Siddig, and Connor Trinneer. Stewart also has a recurring role on American Dad!, which also co-stars Star Trek: Voyager guest star Wendy Schaal. MADtv cast member and DS9 guest star Debra Wilson has also voiced characters on both series. Wallace Shawn voiced Bertram in two episodes of Family Guy. The entire principal cast of Star Trek: The Next Generation appeared as themselves in the episode "Not All Dogs Go To Heaven," in which Stewie abducts them with a homemade transporter to spend the day with them, only to be driven insane by them being extremely difficult.
MacFarlane is a descendant of Mayflower passenger William Brewster, who is an ancestor of 20th century entertainer Bing Crosby – grandfather of Star Trek: The Next Generation actress Denise Crosby. As such, MacFarlane and Denise Crosby are distant cousins. 
The What You Leave Behind expansion of the Star Trek Customizable Card Game features a card of Seth's Enterprise character, giving him the full name of Stewart Rivers, Patriotic Engineer (quite probably referencing his character of Stewie Griffin in Family Guy and his series American Dad).