Ashley Tisdale, Haylie Duff's Kids Have Playdate as Hilary Performs in NYC

Hilary Duff brought her Small Rooms, Big Nerves tour to New York City Tuesday night ... but her sister Haylie was busy hanging out with Ashley Tisdale and their kids following the "toxic" mom group drama.

Check out the snap Haylie posted on her Story Tuesday -- it shows her 7-year-old Lulu playing under a table with Ashley's daughter Jupiter, 4. Ashley showed her seal of approval by reposting the story to her own account.

Notably, it's reported Ashley sold Haylie her Studio City, Calif. home in 2016, so there's some history between the pair. Haylie is now based out of her home state of Texas.

The playdate has fans raising some eyebrows considering the mom group drama that blew up earlier this month when the "High School Musical" alum penned an essay for The Cut about a mean-girl mom circle she decided to quit -- a group fans speculated included Hilary, Mandy Moore, and Meghan Trainor. The chatter about a big falling out only deepened when Hilary's husband Matthew Koma seemingly threw shade at Ashley by mocking her essay on his social media.

But wait ... there's more -- fans have long believed Hilary and Haylie are estranged, considering they haven't been seen together in years. Fans also speculate Hilary wrote about their broken relationship in her new song, "We Don't Talk," which she debuted on her ongoing tour.

Hilary nor Haylie have addressed speculation about their relationship, and Hilary has not confirmed who her new song is about. Meanwhile, Ashley's rep told TMZ fans were looking too deep into her essay, and their theories missed the mark.