The Doctor's Wounded Dragon: The High Garden Dragons 6

Two hearts destined… One impossible choice.
Dr. Adam Richards was raised in a time where being gay was taboo. Like most men of his time, he settled down, married a woman, and had children. Thirty years later, divorced and ready to start over, he wishes he’d been true to himself back when he was younger and desirable. Who’d want an old man like him? And what would his sons think if they knew the truth?
Then Adam meets the young, confident, and gorgeous Aaran MacNair. Adam is positive he’s too old for him. But Aaran has a secret, he’s a thousand year old dragon shifter, and what’s more, he claims Adam is his mate.
A single date quickly spirals into a moment of passion, igniting the bonding process. But Adam’s son interrupts, halting the completion of the bond. Feeling the effects of the mating heat, Aaran has two options—leave or risk killing Adam’s son—both choices have devastating consequences.