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Mycroft decides to try for a baby to carry on the Holmes name. Originally, he was going to do things artificially, until things get sticky and a better offer waltzes right into his lap.
Greg and Mycroft are both single parents, both lonely and overworked, both trying to keep their families together. When they're called up after their children get in a tussle, they find that each other's friendship offers a respite from the toss and turn of their past and present challenges. However, their pups are more than willing to put aside their differences, and offer up something a bit more than friendship as an option.
In a world where everyone is a dom or a sub, Greg has no interest in finding another dom. Unfortunately, he seems to have caught Mycroft's attention, and Mycroft isn't prepared to take no for an answer.