Reading order
| # | Title | Published | Author | Buy on Amazon |
|---|---|---|---|---|
| 1 | Unwrapping the Castelli Secret | 2015 | Caitlin Crews | Buy |
| 2 | The Secret to Marrying Marchesi | 2016 | Caitlin Crews | Buy |
| 3 | The Desert King’s Secret Heir | 2016 | Caitlin Crews | Buy |
| 4 | The Secret Kept from the Greek | 2017 | Caitlin Crews | Buy |
| 5 | Kidnapped for the Tycoon’s Baby | 2017 | Caitlin Crews | Buy |
| 6 | The Baby the Billionaire Demands | 2018 | Caitlin Crews | Buy |
| 7 | Claiming His Hidden Heir | 2018 | Caitlin Crews | Buy |
| 8 | The Secret the Italian Claims | 2018 | Caitlin Crews | Buy |
| 9 | The Heir the Prince Secures | 2018 | Caitlin Crews | Buy |
| 10 | The Italian’s Unexpected Love-Child | 2018 | Caitlin Crews | Buy |
| 11 | The Sicilian’s Secret Son | 2019 | Caitlin Crews | Buy |
| 12 | Shock Heir for the King | 2019 | Caitlin Crews | Buy |
| 13 | The Maid’s Spanish Secret | 2019 | Caitlin Crews | Buy |
| 14 | Sheikh’s Royal Baby Revelation | 2019 | Caitlin Crews | Buy |
| 15 | Cinderella’s Scandalous Secret | 2019 | Caitlin Crews | Buy |
| 16 | Unwrapping the Innocent’s Secret | 2019 | Caitlin Crews | Buy |
| 17 | Proof of Their One-Night Passion | 2019 | Caitlin Crews | Buy |
| 18 | Brunetti’s Secret Son/ Christmas at the Chatsfield | 2015 | Caitlin Crews | Buy |
| 19 | Demetriou Demands His Child | 2016 | Caitlin Crews | Buy |
| 20 | Carrying the Spaniard’s Child | 2017 | Caitlin Crews | Buy |
| 21 | The Greek’s Pleasurable Revenge | 2017 | Caitlin Crews | Buy |
| 22 | The Innocent’s Shameful Secret | 2017 | Caitlin Crews | Buy |
| 23 | The Sheikh’s Secret Son | 2017 | Caitlin Crews | Buy |
| 24 | Demanding His Hidden Heir | 2018 | Caitlin Crews | Buy |
| 25 | Married for His One-Night Heir | 2018 | Caitlin Crews | Buy |
| 26 | The Greek’s Secret Son | 2018 | Caitlin Crews | Buy |
| 27 | The Secret Kept from the Italian | 2018 | Caitlin Crews | Buy |
| 28 | Wed for His Secret Heir | 2018 | Caitlin Crews | Buy |
| 29 | Claimed for the Sheikh’s Shock Son | 2019 | Caitlin Crews | Buy |
| 30 | Demanding His Secret Son | 2019 | Caitlin Crews | Buy |
| 31 | The Italian’s Unexpected Baby | 2019 | Caitlin Crews | Buy |
| 32 | The Sheikh’s Secret Baby | 2019 | Caitlin Crews | Buy |
Secret Heirs of Billionaires is a multi-author Harlequin series built around a single premise: a billionaire discovers he has a secret child. Published between 2015 and 2019, the 32 books feature heroes from Greek tycoons to Italian moguls to desert sheikhs, all facing the same shock of unexpected fatherhood.
The series includes titles like The Secret Kept from the Greek, Claiming His Hidden Heir, and Sheikh’s Royal Baby Revelation. Each book uses the secret heir reveal to bring the hero and heroine back together, often after years apart. The series stands as one of the more popular linked collections in the Harlequin Presents catalog.