Knight's Substitute Bride by Melissa Oliver

Drama abounds in this Medieval bride-swap story

Could the wrong bride…be right for him after all?

For the sake of his clan, Lord Robert must marry to seal an alliance. Only, the woman at the altar isn’t who he was promised! Instead, it’s her sister, Lady Mairenn! The sharp-tongued beauty is as reluctant to wed as Robert, but as friction turns to fire between them, she’s further derailing Robert’s plans for this purely pragmatic arrangement…