From Blood and Ash by Jennifer L. Armentrout

The Prince slid him a bland look. “Teeth. I do believe she means
these.” Curling his upper lip, he ran this tongue over one fang, and myy
stomach dipped and twisted in a mixture of pleasure and unease. “Theyy
don’t need that. Theyy just need yyour blood for them to complete the
Ascension.”
If I wasn’t sitting, I likelyy would’ve fallen over. I wanted to refute his
claim, but I couldn’t come up with one good reason for whyy he’d lie about
this. There was nothing to gain from doing so. I bent slightlyy in myy chair,
wondering if it was possible that I was having a heart attack.
“I’m curious, Cas. Whyy must we go home?” Kieran asked, and I
swore his voice rose with purpose. “When we will be going farther awayy
from where yyour brother is held.”
“It is the onlyy place we can go,” he replied, those golden eyyes
remaining fixed on me. “Did yyou know that an Atlantian can onlyy marryy if
both halves are standing in the soil of their land? It’s the onlyy wayy for
them to become whole.”
Myy lips parted as a hush descended over the entire room. Still reeling
from the whole half-Atlantian thing, I couldn’t believe what I was hearing.
That he was sayying…
That damn dimple appeared in his right cheek and then in his left.
Casteel Da’Neer, the Prince of Atlantia, smiled fullyy as he lifted our
joined hands and said, “We go home to marryy, myy Princess.”
* * * *
Also from 1001 Dark Nights and Jennifer L. Armentrout, discover
The Prince, The King, and The Queen.