David Foster and Katharine McPhee.Photo: Charley Gallay/Getty

Katharine McPheeis enjoying life as a stepmother-to-be!
On Thursday, the 34-year-old singer shared a photo from her Canadian vacation with fiancéDavid Foster, which caught the eye of Foster’s daughterErin, 36, who commented, “CHIC.”
To which, Erin jokingly replied, “I’ve started saying I’m 31, so now she’s 3 years older than me. I’m a problem solver.”
Then, McPhee hilariously chimed in, writing, “@erinfoster stop blowing my age cover! the day we say I do, I’m shipping you and your sister off to Switzerland,” in reference to Erin’s 37-year-old sisterSara.
“Omg you’re gonna parent trap us!!! I knew it,” Erin replied.

Thisisn’t the first timeMcPhee joked around with the Foster sisters.
On Tuesday, theAmerican Idolalum posted a photo from Stuart Island, British Columbia, writing, “Country album drops this week.”
Moments later Erin, who seemed a little left out, commented, “FEELS LIKE I COULD HAVE BEEN INVITED ON THIS BEAUTIFUL TRIP.”
Instead of extending the invitation, McPhee humorously chided: “@erinfoster mommy and daddy need alone time.”
RELATED VIDEO: They’re Engaged! David Foster Proposes to Katharine McPhee During Romantic Italian Getaway
McPhee and Foster, 68, gotengaged in Italy last month, the actress’ rep Leslie Sloane confirmed to PEOPLE.
“He did it at the top of this mountain in Anacapri. Totally dark, only stars,” McPhee explained in a text with Just Jared founder Jared Eng. “Thankfully he didn’t push me off the cliff. He said it was one or the other. And in the end he spared me.”
Jason LaVeris/FilmMagic

The two first darting dating in 2017 and later confirmed their relationship when theystepped out togetherat this year’s Met Gala.
Before the big reveal, McPhee kept their relationshiplow-keytelling PEOPLE she had “zero desire” toaddress relationship rumors.
“Here’s how I look at it: I’m not doing anything wrong, so whether people think it’s true or false… there’s nothing bad happening in my life, so people can just say whatever they want,” she added.
McPhee and Foster have not yet revealed the wedding date.
source: people.com