Bonnie Hut Yaseen, an associate broker at Fox Residential, is used to the youth vote by now. “I’m seeing this trend where parents are coming in to look at my listings and proudly announcing that it was their son or daughter who found it,” she said. “They’re finding an unexpected resource in their children.”

Of course, there is cinematic precedent for all this. In the 1947 classic “Miracle on 34th Street,” a skeptical little girl will believe in Santa Claus only if he can arrange the acquisition of a house she saw in a magazine listing.

Ms. Yaseen said that in the past children saw their homes-to-be only when it was time for the parents to assign them their bedrooms. “Now, in some cases, the kids are coming on the first visit to an apartment because they want to know if it’s as good in reality as it looked online,” she said. “They’ll sometimes be there with paperwork, with a printout from a website.”

Their knowledge can be quite granular. “We had one teenager who knew the specifics of our floor plans. He knew that the C line apartments are 2,296 square feet and that the L units are 2,277,” said Justin D’Adamo, the managing director of Corcoran Sunshine, the marketing and sales team for River & Warren, a condominium development in Battery Park City. “He told his mother that the C line would be better because of his baby grand piano.”

Ultimately, he and his Steinway carried the day.

When Yovanka Bylander Arroyo, a widow with two children, began going to open houses, it was her son, Alexandre, 10, an HGTV and Zillow fan, who asked about square footage and the number of bedrooms and bathrooms. “And I was like, ‘Gee, I don’t know,’ ” said Ms. Arroyo, the executive director of a financial services firm. “Maybe I should be going on Zillow.”

Katie Haggerty, a fashion designer, has worked as a real estate broker. Her mother was a broker, too. She and her husband, Sean, who works in finance, own investment properties. So it makes perfect sense that their three children, most particularly their daughter Patty, 14, have become interested in the ins and outs of the business.