They’re just one big, happy family!David Foster‘s daughters Erin and Sara couldn’t be more thrilled thatKatharine McPheewill be their new step-mom.“They love Katharine, and they’re happy about the engagement,” a source tells PEOPLE of the sisters, who starred in the VH1 reality showBarely Famous.“Of course they joke about the age difference,” the source adds (Erin, 35, and Sara, 37, who are both older than McPhee, 34), “but she’s so sweet and really gets along with the family. She’s spent a ton of time with them. No one has anything bad to say about her.”Cindy Ord/GettyAdds the source: “They love their dad — they jokingly call him a ladies’ man, but they have a good time with it. There’s no bad blood.”This will be the fifth marriage for Foster, 68, and the second for McPhee.In early July, the music producer andWaitressactress announced theirengagementon social media following his proposal on a romantic trip to Capri, Italy. The music producer andAmerican Idolalum first sparked dating rumors last September but didn’t confirm their relationship until they attended the Met Gala together in May.Alison Buck/WireImageFoster’s daughters were some of the first to congratulate the couple — and poke fun at their engagement.RELATED VIDEO: David Foster Talks Katharine McPhee’s “Waitress” Debut: “She’s the New Belle of Broadway”After McPhee and Foster shared the news on Instagram, Erin left a comment in which she called McPhee “Mommmyyy”; later, Sara also got in on the laughs, writing, “Out of the country. What did I miss?”Though they weren’t romantically linked until last fall, Foster and McPhee have been friendly for years — and the Grammy winner actuallyperformed at her first weddingto Nick Cokas in 2008. (She and Cokassplitin 2014, thenfinalized their divorcein 2016.)

They’re just one big, happy family!

David Foster‘s daughters Erin and Sara couldn’t be more thrilled thatKatharine McPheewill be their new step-mom.

“They love Katharine, and they’re happy about the engagement,” a source tells PEOPLE of the sisters, who starred in the VH1 reality showBarely Famous.

“Of course they joke about the age difference,” the source adds (Erin, 35, and Sara, 37, who are both older than McPhee, 34), “but she’s so sweet and really gets along with the family. She’s spent a ton of time with them. No one has anything bad to say about her.”

Cindy Ord/Getty

Saks Hosts Panel Discussion On Power Dressing With Bumble’s Sara & Erin Foster And Designer Andrea Lieberman

Adds the source: “They love their dad — they jokingly call him a ladies’ man, but they have a good time with it. There’s no bad blood.”

This will be the fifth marriage for Foster, 68, and the second for McPhee.

In early July, the music producer andWaitressactress announced theirengagementon social media following his proposal on a romantic trip to Capri, Italy. The music producer andAmerican Idolalum first sparked dating rumors last September but didn’t confirm their relationship until they attended the Met Gala together in May.

Alison Buck/WireImage

2017 GRAMMY Museum Gala Honoring David Foster

Foster’s daughters were some of the first to congratulate the couple — and poke fun at their engagement.

RELATED VIDEO: David Foster Talks Katharine McPhee’s “Waitress” Debut: “She’s the New Belle of Broadway”

After McPhee and Foster shared the news on Instagram, Erin left a comment in which she called McPhee “Mommmyyy”; later, Sara also got in on the laughs, writing, “Out of the country. What did I miss?”

erin-foster-katherine-mcphee-1

Though they weren’t romantically linked until last fall, Foster and McPhee have been friendly for years — and the Grammy winner actuallyperformed at her first weddingto Nick Cokas in 2008. (She and Cokassplitin 2014, thenfinalized their divorcein 2016.)

source: people.com