Dragon Keeper by Minerva Howe

Sloan and his brothers have been happy to live off the grid in the human realm, fighting the forces who would hurt dragons and other paranormal creatures. They never stay in one place too long, so it’s no surprise that things change every time they come back around to familiar places. When they visit their friend Myk’s house in the Colorado mountains, though, they find a whole new world. Literally.
When dragon realm beekeeper Tyr meets Sloan, he knows he’s found his mate for life. But Sloan must work to get both of his brothers to agree to cross the veil and leave everything they know behind. Tyr is worried neither of them will survive until Sloan’s family agrees. And even when Sloan joins him in his world, it’s not the end of their troubles.
Between Tyr’s bees, Sloan’s family woes, and a danger from outside that threatens the children of their village and of Tyr’s family, their road to love is far from easy. Can Sloan find a way to protect everyone, and can Tyr manage to keep his bees and their world together in their shared hive, all while starting a family of their own?