Fifth time’s a charm, right? David Foster, 68, has been dating his much-younger American Idol star girlfriend Katharine McPhee, 33, for just six months, but he’s already “so smitten that he wants to propose,” a source told In Touch. “They’ve tried to keep their romance on the down-low, but they’ve gotten very serious. David’s made it clear that he wants to marry Katharine.”

Luckily for David, Katharine is ready to take things to the next level, too! “[Katharine] wants a child with David,” a source told In Touch. She feels the composer — who already has five daughters — would be the perfect father, says the source, because “David is different than any other guy she’s dated before. He’s a gentleman and has a life. She also finds him very attractive and would love for her kids to have his looks and confidence.” She doesn’t want to waste any time. “She’s practically begging David to make her a mom,” says the source, “and he’s all for it.”

katharine mcphee david foster, getty

To some, that may sound romantic. However, there are definitely some hurdles. David has been married four times before — and not all of his daughters are super supportive of David and Katharine’s huge age difference. Katharine is three years younger than David’s oldest daughter Sara Foster, for goodness’ sake! “David’s daughter Erin [Foster] really likes Katharine, but his other daughters don’t think he should jump into another marriage,” said the insider.

However, Erin and Saran have definitely warmed up to the singer, and gushed about her to E! at the Words With Friends 2 launch on Nov. 9. “We are really happy if our dad is happy,” Sara explained, while Erin admitted “I love her on Scorpion.”

“We love Katharine McPhee. We love our dad. We want our dad to be happy,” continued Sara, who revealed that she’s not bothered by the fact that Katharine is younger than her. “We don’t care who he dates… don’t really care how old they are.” However, the stopped short of confirming the relationship. “We don’t know if it’s her.”

Erin explained that David is a “very young-at-heart kind of guy. Honestly, our friends in their twenties are trying to date him, so we’re just proud of him for not doing that,” she joked. “He’s like, ‘I draw the line there.’ I think thirties, forties is like a respectable age for a man in his sixties.”

Regardless, David’s divorce from Yolanda Hadid was just finalized in May, so it does seem crazy to rush into a new marriage five months later. Katharine has a shaky past with relationships as well. She was married to Nick Cokas when she was caught making out with her Smash director. She filed for divorce seven months later. However, Katharine and David don’t judge each other for past transgressions. They’re totally in love! “They’re really into each other,” said the insider. “They have a very special connection, and if David asked Katharine to marry him today, I think she’d definitely say yes.”

At first, David and Katharine tried to play it cool and keep their relationship a secret, but those days are long gone now. She was his date to his David Foster Foundation 30th Anniversary Miracle Gala & Concert on Oct. 21, and the pair was extra cuddly on the red carpet. Just one day later, she was seen grabbing her boyfriend’s butt while stopping at an ATM back in LA. Clearly, these two can’t get enough of each other.