Fated: Wolf and the Lion by Hawke Oakley

An omega whose never had a heat.
Even in a pack as diverse and quirky as his own, wolf shifter Sage has always been the odd-one out. He’s an adult omega whose never experienced a single heat. But that’s okay with him—he’s content being the funny uncle and the annoying yet lovable youngest brother. That’s enough for him… Right?
When his first heat finally strikes, everything changes. His trusting nature leads him into a dangerous situation—and is saved by a stroke of fate.
The scent of his fated mate.

An alpha whose never had a family.
Xander has always been alone. He left home young, as all mountain lion shifters do, but Xander had another reason to run. His fathers, a mountain lion and a wolf, never got along. He’s convinced their pairing was a mistake—that all pairings are. As much as he wants a baby, he’s never going to risk giving a child an unhappy home.
Bad luck follows Xander everywhere. When he runs across a thorny situation, he’s forced to save a stranger, an omega wolf with a smile bigger than his brain. But when that alluring scent comes wafting off him, Xander refuses it.
It’s not possible for a wolf to be his fated mate. Two predators of different species can’t be fated mates. And there’s no way an irritating little omega is going to prove him wrong.