Too Scot to Hold by Caroline Lee

The battle to determine the next laird comes down to this fierce moment…the Oliphant brothers sitting around, drinking ale, while their wives go into labor.
After finishing his studies to become a doctor, Graham followed the woman he loved to Oliphant Castle and discovered—among other things—that he was not the fatherless, family-less bastard he’d always assumed. Well, he was still a bastard, but now he was an Oliphant bastard; he had father who loved him, and six brother who cared as fiercely as they fought. He’d found a home.
And he might’ve been happy, had Davina MacKinnon been allowed to share it with him. But her grandfather has never seen him as good enough for her, or the future of the MacKinnon clan, and despite her sister’s marriage to one of Graham’s brothers, Davina was dragged away.
But now she’s returned to be with her sister during her confinement, and Graham—being a medical man—has been called back to Oliphant Castle as well, to help with all the bairns about to be born. Whichever Oliphant wife births the laird’s first grandson will ensure her husband becomes the next laird, so the stakes are high…But none so high as Graham and Davina’s.
Between the bairns popping out left and right (seriously, this is getting ridiculous), they’ve got to find a way to convince her grandfather they deserve to be together. Luckily, there’s a way to distract the old man, and the Ghostly Drummer of Oliphant Castle might just make a comeback…