THE ABYSS: BLOOD KIN BOOK 1
A space marine falls in love with alien vampire.
Being half-vampire gives space marine Anarion Gray powers that none of the other marines have, but they also isolate him from the rest of humanity and vampire kind, too. Except for the vampire leader, Lord Abaddon.
When he serves on board the vampire flagship, The Abyss, he discovers that Abaddon wants him for more than just being the first--and potentially only--human-vampire hybrid.