Twins For The Rebel Cowboy by Sasha Summers

Accidental family?

For one crazy night, Annabeth Upton lets loose to forget her worries: Grandma Flo's medical bills, little Cody's stutter, the challenges of being a school principal and a single mom. Then Ryder Boone steps in to protect her from a rowdy bar patron…and in a hot half hour they create the biggest worry of all. Two of them, actually! 

Ryder was always the rebel of the Boone family, but he does the right thing and proposes. Annabeth says yes–but thinks the marriage is temporary, meant to save her from scandal. The last thing she wants is to force Ryder into a loveless marriage forever, so she gives him an opt–out clause. The only problem is that as they grow even closer, she doesn't want him to leave!