Alpha's Luna is a Fae-Siren Mage!

When the alpha (her 1st mate) saw her, he quickly rejected her, thinking she was a human girl. But no, she isn't. She is a siren-the last and most powerful one to ever exist. Her second chance mate is also an alpha, and he does the opposite of her first mate. However, she cannot produce him an heir after 5 years. Will she be able to tell him her secret and why she is barren?