Katherine Heigl is pregnant

In a statement, they shared: "The Kelley clan is thrilled to announce that we are expecting a third addition to our family. Naleigh and Adalaide could not be more excited to welcome their new sibling into the fold and Josh and I are overflowing with joy and gratitude.

"This is an incredibly exciting time for us filled with hope, anticipation, and hormones. Well, only I'm filled with hormones, but everyone in the family gets to enjoy them. We couldn't be more excited to be able to finally share this news with our fans and are looking forward to continuing to share the journey with you all. xoxo, Katie and Josh."

The new arrival - who is due in January 2017 - will join his adopted siblings Adalaide, four, and Naleigh, seven.

Meanwhile, the 37-year-old actress previously revealed motherhood has given her "perspective."

She said: "It's been a huge blessing - it gave me perspective. Before them, it was all about my goals as an actor. They helped me to take a step back and go, OK, I have some important work to do on this earth.

"Naleigh is going on 13! She's very sassy and confident.

Adalaide's a total tomboy who's obsessed with bugs. The other day she was digging for worms."

And Katherine went on to praise Josh, 36, for being a "fantastic" father.

She added: "He gets up with them in the morning more often than me. I am not a morning person. The girls are obsessed with him. I think that every woman with healthy self-esteem had a really great dad."