Find That Book

Genre: Horror romance? Romance? Given when I read this, it could have been a romance novel aimed at adults or it might have been aimed at older teens. Generally, a pulpy sort of book. 

CONTENT NOTE: This book has cannibalism and incest. 

General plot: A young woman (our view point character and protagonist) takes a job( or for some other reason?) goes to live at a large rural home of stately history. She's a very Gothic heroine - her mom seemed to have no family and no history, and the protagonist is on her own. She goes to live in this large manor/plantation, where an stately old woman and two much younger, hot, brothers live together. The protagonist thinks they are grandsons of the old woman, but it's not clear. She feels oddly like this mansion/plantation home is somewhere she knows before, or should have been before. There's a strong Gothic tone to the setting - the protagonist is always overhearing cryptic conversations that don't make sense.

In the romantic plot, the two brothers are both attractive and seem to be attempting to woo the protagonist, but at least one of them seems to be having (somewhat kinky, bitey) sex with the matriarch character. The protagonist is confused and scared by this - she thought they were related??

The resolution of the plot is that BOTH the brothers are actually immortal, unaging, and under a curse - they were in a love triangle with a woman hundreds of years ago, and instead of handling it, they murdered/dueled each other and the woman they loved did some kind of magic/curse, so they are now immortal, and the three of them entered into a triad relationship. (The time setting for this MIGHT have been the Civil War?)

They are also cannibals??? There's a plot point where they also eat their girlfriend to survive, but uh, she somehow doesn't die?  

As time passed, the trio had a daughter, and when the daughter grew up, welp. The brothers started having a relationship with her - meaning that, in the present day, we are several generations into a cannibalistic, incestuous, undead threesome, all centered around this plantation house. And, of course, the protagonist is actually part of this family- the matriarch is her grandmother. Her mother was supposed to be the next in line for this triad, but she fled and made her own life elsewhere. (I cannot remember if the protagonist was born there and taken, or if she is the result of the mom having married someone else and he just happened to be out of the picture. - I suspect the former.) The brothers have magically summoned her back to the plantation home to continue the family together. 

The ending of the book is that the protagonist accepts her role, seems relieved to not have to choose between the brothers, they have not-super-explicit sex, and, in a time jump, is shown to have had a toddler who is playing in the gardens of this mansion with her fathers. 

Specific scene memories: 
-The protagonist, while eavesdropping, sees one of the hot brothers kissing and biting the neck of the older woman, who is clearly into it, but it's also kind of vaguely vampiric in tone and the protagonist can't figure out if she's actually being injured.
-One of the brothers, explaining the whole curse situation to the protagonist, proclaims "There is not even a word for what we are." Because, well, immortal brothers in a curse that makes them periodically eat their girlfriend. 
- I vaguely remember the protagonist is generally FINE with the ending, and feels calm and at peace with her unusual choices. 

I do not know if they book is GOOD, but I was trying to describe this plot to someone in a discussion of Gothic romance, and since I couldn't remember the book, I now feel compelled to try and find it to prove that I did not make it up.