This probably made Fergie's day! 

Josh Duhamel shared the sweetest snap via Instagram of him holding their baby boy, Axl Jack, with a birthday note for the Black Eyed Peas singer.

"Happy Birthday Mommy!!!," the sign read, which Josh held up while holding their wide-eyed adorable little guy. 

The blonde beauty turns 39-years-old today, and we're sure the sweet message from her hubby and their baby made her birthday extra special! 

Fergie isn't the only family member celebrating a birthday this week -- Axl will will turn 7-months-old on Saturday! 

We can't wait to see more pictures of this little stud -- who do you think Axl looks like more? Tell toofab in the comment section below and click "Launch Gallery" above to see even more cute celebrity kids! 

Happy birthday Fergie!