Something Fabulous by Alexis Hall

From the acclaimed author of Boyfriend Material comes a delightfully witty romance featuring a reserved duke who’s betrothed to one twin and hopelessly enamoured of the other.

Valentine Layton, the Duke of Malvern, has twin problems: literally.

It was always his father’s hope that Valentine would marry Miss Arabella Tarleton. But, unfortunately, too many novels at an impressionable age have caused her to grow up…romantic. So romantic that a marriage of convenience will not do and after Valentine’s proposal she flees into the night determined never to set eyes on him again.

Arabella’s twin brother, Mr. Bonaventure “Bonny” Tarleton, has also grown up…romantic. And fully expects Valentine to ride out after Arabella and prove to her that he’s not the cold-hearted cad he seems to be.

Despite copious misgivings, Valentine finds himself on a pell-mell chase to Dover with Bonny by his side. Bonny is unreasonable, overdramatic, annoying, and…beautiful? And being with him makes Valentine question everything he thought he knew. About himself. About love. Even about which Tarleton he should be pursuing.
 
- Goodreads Summary