Richard Castle is played by actor Nathan Fillion.
Richard Castle is the son of Martha Rodgers and father of Alexis Castle. He has been married twice before, first to Meredith, Alexis' mother and later to his Publisher Gina Cowell. Castle does not know who his father is.
Changed his name from Richard Alexander Rodgers to Richard Edgar Castle when he became an author. Edgar is in reference to Edgar Allan Poe.
Castle's first novel was In A Hail of Bullets and was published while he was still in college . It won the Nom DePlume Society's prestigious Tom Straw Award for Mystery Literature. In Last Call, Castle tells Kate Beckett that he wrote the book in a booth at a well-known bar for writers called "The Old Haunt" which Castle buys later in the episode.
Castle is best known for his Derrick Storm series.
He wrote his first book, In a Hail of Bullets while sitting in a booth in a famous writer bar dating from the late 1800s called The Old Haunt. A portrait of him hangs in the bar over the booth.
Involvement with the NYPD
Castle started helping the NYPD solve crimes when he caught their attention as a suspect after several murders resembled scenes from his novels. After the case was solved Castle pulled in a favour from the mayor and was allowed to shadow Detective Beckett to do research for his book. After his first book was published Castle was considering taking on a new project but his publisher offered him a contract to write three more Heat novels.
Nikki Heat Series
Castle gets the inspiration for Nikki Heat from New York City Detective Kate Beckett who he started shadowing, with his friend the Mayor's permission, after Detective Beckett questioned him regarding copycat murders taken from his previous works. Castle also created characters based on Beckett's friends and colleagues and his mother.
In addition to his two marriages we know Castle to have been involved with several women.
In episode 2.12 (A Rose Forever After), Castle reconnects with his old college flame and first love, Kyra Blaine when they investigate the murder of one of her bridesmaids. She and Castle met in college and dated for three years before Kyra told him she needed space and traveled overseas. The breakup clearly left him very hurt and may be the reason why his two marriages failed. As he says in the episode, his marriages "seemed like the right thing to do at the time." Beckett describes her as "real" and therefore, unlike Castle's two ex-wives. As the investigation progresses, Castle believes Kyra's fiancee had something to do with the murder, but he and Beckett eventually discover that her fiancee was not responsible, and though tempted, did not cheat on Kyra.
When he appears in the New York Ledger's Ten Most Eligible Bachelor list, Castle hooks up with most eligible bachelorette #3, but during the date he's distracted by Beckett and the case they're working on so things don't work out.
Castle has a fling with his first ex-wife Meredith, mother to Castle's daughter Alexis, but refers to her as a "Deep Fried Twinkie" (guilty pleasure that you can only have once in a while) and as a crazy person who prevents him from re-forming a serious relationship with her.
Castle's second ex-wife, also his publisher, is Gina Cowell. After he watches Beckett form a serious relationship with Detective Tom Demming and turn down his invitation to join him at his house in the Hamptons for the summer, he reconnects with Gina and ends up spending the summer with her (episode 2.24, A Deadly Game). When he returns to the precinct in the fall, they are still together. However they have a loud argument (described by Martha as a PDA: public display of anger), the newspaper writes a story about this which is how word gets around the precinct. Gina calls Castle's phone numerous times, but he refuses to answer and even resorts to 'magic' to make it disappear. He finally accepts the call and Beckett overhears Castle breaking up with Gina.3.12
Richard Castle on Marriage...
- Castle states: "Betrayal, Lies and Deceit - Sounds like my first marriage."
- Detective Ryan also asks Castle once, regarding sex: "Between you and me, you ever pay for it?" to which Castle responds "Are you counting my marriages?"
Hobbies & Interests
His safe word is apples, his favorite holiday is Halloween, and he enjoys playing laser tag, guitar hero and basically enjoys acting like a child. He is fascinated by gadgetry like onion goggles and "apped" up cell phones.
He also enjoys playing poker and often plays with other famous and successful novelists like James Patterson, Stephen J. Cannell and Michael Connelly.
Having written his first book in a bar, he enjoys bar culture and knows quite a bit about the Prohibition Era.
Being a writer, he also is fascinated with the occult, aliens, unexplained phenomena, and spies, all of which run directly counter to Beckett's more rational way of looking at crimes.
He wears a bulletproof vest that he specially ordered with the word "WRITER" printed across it. 
Richard Castle has an official Twitter account @WriteRCastle.