As older sister Jessica Simpson was recovering from giving birth to baby boy Ace Knute Johnson, Ashlee spent some quality time with her own son Bronx.

The singer hit the beach with her four-year-old on Sunday. Her ex-husband Pete Wentz, who took his own beach trip with Bronx in Miami in June for his 34th birthday, was nowhere in sight. However, the mother-son duo was accompanied by a mystery man who followed close behind. Ashlee is back on the market so maybe she's dating again! She ended her relationship with Boardwalk Empire actor Vincent Piazza late last year.

Ashlee was dressed for the Malibu sun in a beige pleated maxi dress, straw sun hat, and large, round-framed sunglasses. Curly-haired Bronx looked adorable in a white tee and orange trunks.

It's a bit odd that the "Pieces of Me" singer isn't by her sister's side following her C-section. Then again, this isn't Jessica's first rodeo. She's already mother to one-year-old daughter Maxwell.