David Foster and Katharine McPhee got engaged during a trip to Italy in July 2018

By Helen Murphy
February 13, 2019 11:30 AM

David Foster‘s daughters have a good sense of humor about his upcoming wedding to Katharine McPhee.

After seeing an article that claimed Foster, 69, and McPhee, 34, were planning a $50 million wedding, Foster’s daughter, Erin, 36, posted a screenshot of the page to Instagram, captioning the image “There’s [sic] goes my inheritance.”

In an exchange captioned by Comments by Celebs, Erin’s sister Sara Foster, 38, commented on the post writing, “Our inheritance was gone a long time ago FYI.”

McPhee showed her solidarity in the comments, writing “There goes mine too tbh.”

McPhee and Foster got engaged in July. After dodging relationship rumors for months, they confirmed that Foster had proposed with a sparkling emerald-cut diamond ring while they vacationed in Anacapri, Italy. The pair has not yet revealed their wedding date.

The couple has been friends for years — first meeting on the set of American Idol when McPhee was a contestant in 2006.

Rob Latour/Variety/REX/Shutterstock

Since her father and McPhee went public with their relationship, Foster’s daughters haven’t been afraid to tease their dad about his engagement with their soon-to-be stepmom.

Erin left a comment on her dad’s Instagram post from his vacation with McPhee to Italy in July, calling her soon-to-be stepmom, “Mommmyyy” (alongside a sea of heart emojis). Sara also got in on the laughs, writing, “Out of the country. What did I miss?”

In December, Erin commented on a sun-soaked photo of McPhee wearing a yellow bikini, writing, “Grandma!!!! Wtf I don’t want to be next to you at the pool,” Erin said in a message first spotted by Comments by Celebs.

Katharine McPhee Instagram

McPhee then hilariously poked fun at herself by replying, “@erinfoster Grandma carries it in the back. Don’t worry- you’ll see my cellulite when I stand up.”Foster has five daughters — Sara, Erin, Amy, 45, Jordan, 32, and Allison, 48. RELATED: David Foster Admits He ‘Won the Lottery’ as Katharine McPhee Says She ‘Can’t Wait to Marry’ Him

Sara posted another bikini photo of McPhee in December, captioning the post, “When your mom refuses to dress age appropriately.”

In response, the singer quipped, “I can’t even think of a good response.” This prompted Sara to reply, “As long as you keep looking this good in a bikini, I will be writing captions like these.”

Sara Foster/Instagram

McPhee and Foster opened up to PEOPLE about their journey to love in September. “We genuinely love and respect each other and have for a very long time,” McPhee said.

“She didn’t catch my eye on the first day because I was so busy trying to do my job,” added David. “But the reality is that in the last 12 years I’ve always had a connection with her.”