It's been a year since Jessica Simpson became an aunt to Ashlee's son, Bronx.

"Happy Birthday to my precious angel on earth!!! Bronx is 1 today!! I LOVE HIM SO MUCH!!!" Jessica wrote on Twitter Friday.

Check out adorable photos of star kids bundled up

"I can't believe it has been a year already," she continued.

Her little sister Ashlee wrote her own message on Twitter Thursday.

"BX's 1st bday tomorrow! My angel is going to be a year!! The greatest year of my life :)" she posted.

Her husband, Pete Wentz, added, "happy birthday bx. you dont have twitter and cant read this. thanks to all my friends that recorded lullabies. cant believe its been a year."