SOLVED. Romantic book about angels. [s]

[Aymara]

So I read this book a few years ago, like 5 years i'd say. It was about two angels who where on Earth that didn't remember being angels, and thought they were human, brother and sister. They actually were lovers and guarded the doors of heaven or something like that. I think the devil put them on Earth cause he knew they were too powerful when they were together and he knew if they thought they were brother and sister they wouldn't do anything about the attraction they feet towards each other. They eventually find out. I don't remember the title or the author, I thought it was "forbidden" but it wasn't.

[Rosa]

Aymara, how is it different from Forbidden? It sounds almost exactly like it.

[Rosa]

Is it one of the Mortal Instruments books?

[Aymara]

Yes, it's forbidden! Thank you!! When I googled "forbidden" the only one that came up was the one by Tabitha Suzuma.

[Rosa]

Great!