Ne-Yo is to become a father for the fourth time.

The 'So Sick' singer's wife Crystal Smith has revealed she is expecting the couple's second child after they welcomed son Shaffer into the world in May 2016.

She gushed: ''We are so excited! This definitely wasn't in the plan and we weren't trying at all!''

And Crystal knows Ne-Yo's other children - Mason and Madilyn, both six, who he has with actress Monyetta Shaw - will be thrilled about the family growing in size.

She added: ''They're going to be so excited. Maddie has asked a few times for a little sister since having SJ so fingers crossed.''

And the happy couple already have some baby names in mind for their little one.

She shared: ''This gender reveal party is going to be epic. We have had names for our angels since before Shaffer Jr. was born so, yes, we are all set on baby names.''

Crystal has been having lots of cravings throughout the first trimester of her pregnancy and insists that, despite being vegan, she will ''eat all the meat in the world'' for her baby boy or girl if she needs to.

She told E! News: ''Actually I haven't really been sick at all but the cravings are real! All I want are raw oysters and steak! Which since becoming vegan has totally messed up my diet but as long as our miracle gets the nutrition it needs I will eat all the meat in the world!''

Ne-Yo also confirmed the news in a post on social media.

Alongside a picture of his three children and then a question mark in the fourth box, he wrote on Instagram: ''Sooooooo..... guess who's awaiting a NEW ARRIVAL!?! @itscrystalsmith and yours truly are happy to announce we are expecting! #NewAddition #ExtendingTheFamily (sic)''