Katharine McPhee wears matching swimsuits with her stepdaughters Sara and Erin Foster on family trip

Katharine McPhee showed off her incredible post-baby body in a tie-dye one-piece, designed by stepdaughter Sara Foster, during a family getaway to Turks and Caicos. 

While holding her one-month-old baby boy Rennie, the 37-year-old Smash actress was surrounded by loved ones, who sat on the same lounge chair and posed in matching pastel swimsuits. 

Two of David Foster daughters, who he shares with ex-wife Rebecca Dyer, Erin, 38, and Sara, 40, were pictured with McPhee as they smiled brightly into the camera. 

Matching: Katharine McPhee showed off her incredible post-baby body in a tie-dye one-piece, designed by stepdaughter Sara Foster, during a family getaway to Turks and Caicos; Erin Foster on the left and Sara Foster on the right

Earlier this week, McPhee shared a bathroom mirror selfie in the $125 beach-ready design, which she described as the ‘best one-piece’ she’s ‘ever tried.’

‘Usually it’s cut too low and the torso isn’t long enough – straps are adjustable. So comfortable! You nail it @sarafoster,’ she praised on her Instagram Story. 

In the image, taken just five weeks after giving birth, the former American Idol contestant oozed confidence as she displayed her very lean stomach and tan legs.  

Looking good: Earlier this week, McPhee shared a bathroom mirror selfie in the $125 beach-ready design, which she described as the 'best one-piece' she's 'ever tried'

Looking good: Earlier this week, McPhee shared a bathroom mirror selfie in the $125 beach-ready design, which she described as the ‘best one-piece’ she’s ‘ever tried’

Designer: Sara has posted a number of photos of herself, husband Tommy Haas and their two daughters Valentina Haas and Josephine Lena Haas on her Instagram account

Designer: Sara has posted a number of photos of herself, husband Tommy Haas and their two daughters Valentina Haas and Josephine Lena Haas on her Instagram account

Sara has posted a number of photos of herself, husband Tommy Haas and their two daughters Valentina Haas and Josephine Lena Haas on her Instagram account.  

She is one of five adult children that McPhee’s husband David Foster has from his previous relationships. 

The prolific music producer, 71, is also a dad to daughters Allison Jones Foster, 50, who was born when he was 20 and placed for adoption only to reconnect thirty years later, and Amy Skylark, 47, from his first marriage to B.J. Cook. 

Daddy: Sara, 40, is one of five adult children that McPhee's husband David Foster has from his previous relationships. He's pictured with Sara in October 2019

Daddy: Sara, 40, is one of five adult children that McPhee’s husband David Foster has from his previous relationships. He’s pictured with Sara in October 2019

Couple: Singer and actress Katharine married David, 71, in 2019 and they welcomed their son Rennie on February 24 (pictured together in 2019)

Couple: Singer and actress Katharine married David, 71, in 2019 and they welcomed their son Rennie on February 24 (pictured together in 2019)

David and singer and actress Katharine married in 2019 and welcomed their son on February 24.

Earlier this week, Katharine proudly showcased her figure in a brown one-shoulder bikini and told her social media followers that she ‘loves’ her new curves and ‘being a mommy.’ 

The photos come after Katharine insisted to People in March that she didn’t feel any pressure to ‘bounce back’ or ‘fit into her jeans’ following her pregnancy.  

Loving her curves: Earlier this week, Katharine had shown off her post-baby body as she posed in a brown one-shoulder bikini for a mirror selfie in her bathroom

Loving her curves: Earlier this week, Katharine had shown off her post-baby body as she posed in a brown one-shoulder bikini for a mirror selfie in her bathroom

Happy: The American Idol alum told People in March that she didn't feel any pressure to 'bounce back' or 'fit into her jeans' following her pregnancy

Happy: The American Idol alum told People in March that she didn’t feel any pressure to ‘bounce back’ or ‘fit into her jeans’ following her pregnancy

‘I’ve just been so grateful and happy that I’ve had a healthy baby and I’ve felt really good, emotionally and physically,’ she told the outlet.

‘I’m so happy that I don’t have this crazy pressure yet to fit into whatever jeans I have in my closet. I don’t even think about them right now!’ 

The new mom added that it’s ‘nice to have a break’ from working out, too. 

She mused: ‘In my everyday life, I would have an event coming up or need to work out and it’s just really nice to have a break and be happy where I am.’  

Relaxed: Katharine insisted to People in March that she didn't feel any pressure to 'bounce back' or 'fit into her jeans' following her pregnancy. 'I've just been so grateful and happy that I've had a healthy baby and I've felt really good, emotionally and physically,' she told the outlet

Relaxed: Katharine insisted to People in March that she didn’t feel any pressure to ‘bounce back’ or ‘fit into her jeans’ following her pregnancy. ‘I’ve just been so grateful and happy that I’ve had a healthy baby and I’ve felt really good, emotionally and physically,’ she told the outlet