Thomas Luke Casteel, is the son of Toby and Annie Casteel, husband of Leigh VanVoreen, Sarah Casteel, and Stacie Casteel, and father of Tom, Fanny, Keith, Jane and Drake Casteel as well as step-father of Heaven Casteel and grandfather to Darcy Wise and Luke Casteel Jr as well as Great-grandfather to Annie and Luke Casteel Jr's children.He is infamous for selling all his children (with the exeption of Drake) to different couples in the first book.
Luke comes and goes quite often, not being a strong father-figure to his family. He dotes and spoils Fanny, while he completely ignores Heaven. Luke's mother Annie explains to Heaven that she reminds him too much of Heaven's birth mother, Leigh. He goes to a whore house called Shirley's place and drinks as well as losing his temper and arguing with Sarah and eventually coming and going often. After he contracts a sexual illness, his wife gives birth to a stillborn and blames Luke for it for having sex with other women and eventually abandoning him and the kids. Luke sells his children off to various people. He sells Heaven to a former girlfriend of his, named Kitty Dennison. Kitty became pregnant by Luke while a teenager, she had an abortion, which left her unable to have anymore children.
After Heaven leaves the Dennisons, she sees Tom, who tells her that Luke has become a changed man, no longer having sex with other women and drinking and gambling, met a woman named stacie and has a baby son with her, Drake and eventually becomes the owner of a circus, his big dream since he was a child.
Luke invites Heaven via letter to come live with him, promising to treat her better than before, Heaven however was unable to forgive Luke and instead goes to Boston to live with her grandparents.
Luke appears briefly when Heaven turns up at a his circus and runs away when she doesn't want him to see her. She then dyes her hair blonde so Luke can except her as his daughter, despite finding out that Tony Tatterton, her step-grandfather, is her biological father following his rape of Heaven's mother, Leigh.
When she turns up during a lion taming show and Tom is working there as a circus clown, Luke sees her and mistakes her for Leigh, causing him to get distracted and the lions run loose and start mauling Luke, however Tom jumps in to save him, getting killed by the lions in the process.
After Toby Casteel dies, Luke tells Heaven that she is always welcome at his and Stacie's house. Luke even becomes a grandfather when Fanny gives birth to Reverand Wise's baby, Darcy.
Luke doesn't make another appearance. He writes to Heaven telling her that he can't come to her wedding to Logan Stonewall. Later in the next year, Heaven and Tony get a telegram telling them that Luke and his wife Stacie have been killed in a car accident on the highway. After Luke and Stacie's funeral, Heaven takes in Drake. When living at Farthy, Heaven finds an agreement between Tony and Luke that Luke can keep ownership of his circus on the condition that he never contacts Heaven again, leading Heaven to realize that Luke had 'sold' her again.
Luke's grandson from Fanny is born at the end of the novel and named after him.