The singer, actress and fashion designer joined her three kids and husband Eric Johnson to celebrate the latter’s newest age milestone earlier this week, when the family of five sat outside together in front of a cake that proclaimed “Happy 40th!” written in green frosting.
The birthday boy was the only one looking at the camera, though, as 7-year-old Maxwell Drew posed with her chin on her hand and glanced outside the frame while Simpson, 39, and son Ace Knute, 6, looked at baby Birdie Mae.
Despite the festive nature of her adorable frilly white outfit and matching bow, the infant — who turns 6 months old on Thursday — proved that no baby moment is predictable, sporting an unmistakable cry face as her head was tilted forward toward the cake.
“Not everyone’s all smiles about dad turning 40 😜,” Simpson quipped in the caption.
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Birdie’s smiley snapshots have far outweighed the grumpier ones on Simpson’s Instagram account since she and Johnson, a former NFL tight end, welcomed her into the family on March 19.
Last week, the “I Wanna Love You Forever” singer shared a black-and-white image of her and her baby girl tossing matching wide grins at the camera, with Birdie wearing a knotted head wrap as she leaned against her mama.
“While the other 2 kiddos are off at school, this little lady and I snuggle a lot 🥰😍💚 #BIRDIEMAE,” Simpson wrote in the sweet photograph’s caption.
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In an exclusive chat with PEOPLE this past July, Simpson said there was “a lot of dividing and conquering going on” in their family at the moment to keep everything running smoothly with three kids.
“It is definitely constant, and the biggest challenge for me is trying to be present when I am pulled in so many directions,” said The Dukes of Hazzard actress. “They are all in such different phases now.”
However, Simpson added that she and her husband make it a priority to take one night a week to themselves, handing Maxi and Ace off to Johnson’s parents and hiring a babysitter to take care of Birdie.
“We typically download a movie and order dinner or do something super low-key to just connect,” she told PEOPLE. “Eric is the greatest motivator and connecting with him on morning walks is the most grounding part of my day.”