SOLVED. YA series. Piece of earth breaks off and floats in sky as own kingdom [s]

[Becca]

I read this book within the past year. I remember scattered bits and pieces, sorry in advance. I'd really appreciate any help.
A piece of earth breaks off and is floating in the sky.
The main character is a young girl whose brother jumped over the edge and is now blind and isalso a part of a resistance group.
They end up tunneling through the bottom of the floating kingdom and landing on earth where they find their princess has stowed away on the ship.
They start living with the policeman whi found them and his children.
There's a bombing and one of the kids die at the harbor that they'd snuck out to go to.
One of the kids was nicknamed birdie.
The main character comes to find out their wedding bands, which are hollow and filled with the betrothed's blood, are really a fuel system the earth needs to win a war.

Please help me find this series! Thank you!

[Lou]

Perfect Ruin

[Becca]

Perfect! Thank you!