Phoenix Prince by TJ Nichols

Prince Everest of Mont de Leucoy—heir to the throne, spy, and double agent—is determined to rescue his brother who was captured over two hundred years ago, even if he destroys himself in this life.

Everest has spent his last two lives planning and setting up this mission. But to act on the plans he made last time, he invoked a dangerous magic, and now, as he is so close to success, he is running out of time to save his brother and heal the soul bruise that the loss caused.
As the prince’s bodyguard, Cadel McKeon has one job: protect the prince. He never expected to disobey the king or to agree to rescue another phoenix from the Shadow Board in a foreign country. But if he doesn’t help Everest, then everything he set up will be wasted, and Cadel can’t sit back and watch the brilliant and wounded young man fail.
Now, he has a second job: keeping Everest in the present as his mind crumbles under the weight of the past. Neither job is easy, especially when Everest’s plan is to be captured by what remains of the Shadow Board.

Getting in was the easy part…getting out alive…was never part of Everest’s plan. To save them all, Cadel will need the help of the brothers who no longer trust Everest.

Phoenix Prince is book 4 of the Brothers of Fire series about the royal phoenix shifters of Mont de Leucoy. If you love mm fated mates, past lives, princes, and spies, join the phoenixes.