Evolution

The Darkwood Alpha siblings struggle to survive and coexist after the eldest Coen is mated to a day-walker, a wolf-vampire hybrid. His siblings, Callen and Camillia, accept Trinity is their brother's mate, but many in Darkwood Pack and beyond to the vampire royal court do not. To survive, all must change, but some refuse to accept the truth of Evolution.
During, and in the decades after the Fifth Great War, there were massive population declines, leaving large areas unpopulated, and a society feigning a return to normalcy. Children are now the most valuable commodity in a world where the Infant Plague ends half of all pregnancies before birth and kills two-thirds of the infants born in their first year, sometimes taking the mother with them. Hybrid children of mixed human, wolfen, vampire, or fae lineages fare better than pure-blood, single species children, but prejudice and hate would rather see extinction than evolution.

Shifter Tropes in this story - Fated Mates - Telepathic Pack and Mate Link - Hybrids