Reading order
| # | Title | Published | Author | Buy on Amazon |
|---|---|---|---|---|
| 1 | Unwrapping the Castelli Secret | 2015 | Dani Collins | Buy |
| 2 | Brunetti’s Secret Son/ Christmas at the Chatsfield | 2015 | Dani Collins | Buy |
| 3 | The Secret to Marrying Marchesi | 2016 | Dani Collins | Buy |
| 4 | Demetriou Demands His Child | 2016 | Dani Collins | Buy |
| 5 | The Desert King’s Secret Heir | 2016 | Dani Collins | Buy |
| 6 | The Sheikh’s Secret Son | 2017 | Dani Collins | Buy |
| 7 | The Innocent’s Shameful Secret | 2017 | Dani Collins | Buy |
| 8 | The Greek’s Pleasurable Revenge | 2017 | Dani Collins | Buy |
| 9 | The Secret Kept from the Greek | 2017 | Dani Collins | Buy |
| 10 | Carrying the Spaniard’s Child | 2017 | Dani Collins | Buy |
| 11 | Kidnapped for the Tycoon’s Baby | 2017 | Dani Collins | Buy |
| 12 | The Greek’s Secret Son | 2018 | Dani Collins | Buy |
| 13 | The Baby the Billionaire Demands | 2018 | Dani Collins | Buy |
| 14 | Claiming His Hidden Heir | 2018 | Dani Collins | Buy |
| 15 | Demanding His Hidden Heir | 2018 | Dani Collins | Buy |
| 16 | The Secret the Italian Claims | 2018 | Dani Collins | Buy |
| 17 | Wed for His Secret Heir | 2018 | Dani Collins | Buy |
| 18 | The Heir the Prince Secures | 2018 | Dani Collins | Buy |
| 19 | The Italian’s Unexpected Love-Child | 2018 | Dani Collins | Buy |
| 20 | Married for His One-Night Heir | 2018 | Dani Collins | Buy |
| 21 | The Secret Kept from the Italian | 2018 | Dani Collins | Buy |
| 22 | Demanding His Secret Son | 2019 | Dani Collins | Buy |
| 23 | The Sheikh’s Secret Baby | 2019 | Dani Collins | Buy |
| 24 | The Sicilian’s Secret Son | 2019 | Dani Collins | Buy |
| 25 | Claimed for the Sheikh’s Shock Son | 2019 | Dani Collins | Buy |
| 26 | Shock Heir for the King | 2019 | Dani Collins | Buy |
| 27 | The Maid’s Spanish Secret | 2019 | Dani Collins | Buy |
| 28 | Sheikh’s Royal Baby Revelation | 2019 | Dani Collins | Buy |
| 29 | Cinderella’s Scandalous Secret | 2019 | Dani Collins | Buy |
| 30 | Unwrapping the Innocent’s Secret | 2019 | Dani Collins | Buy |
| 31 | Proof of Their One-Night Passion | 2019 | Dani Collins | Buy |
| 32 | The Italian’s Unexpected Baby | 2019 | Dani Collins | Buy |
Secret Heirs of Billionaires is one of Harlequin’s longest-running continuity series, with thirty-two books published between 2015 and 2019. The shared premise — wealthy men discovering they have secret children — provides the framework, while individual authors bring their own characters and settings. Greek, Italian, Spanish, and Middle Eastern billionaires all discover hidden heirs across the collection.
Dani Collins is one of many authors who contributed to this series. The books work as standalone romances within the shared concept, each featuring a different billionaire and a different secret child revelation.