Ashlee Simpson and Bronx's Bikini Beach Day

Posted Sunday December 30, 2012 9:45 AM GMT

Joining the rest of the clan, Ashlee Simpson headed to Hawaii to spend some holiday vacation. On Saturday, the 28-year-old singer headed to the beach on Oahu to soak up the sun and play in the surf with her son, Bronx, and some friends.

Looking great in a black and white bikini and burgundy New York Yankees baseball cap, the doting single mother kept a tight hold of her 4-year-old in a blue life vest.

Meanwhile, her sister Jessica took the opportunity while in the Aloha State to announce that she's expecting her second child with husband Eric Johnson.

The Weight Watchers spokesperson posted a photo of baby Maxwell on Twitter on the beach with "Big Sis" scrawled in the sand.

Photo Credit: FameFlynet.com