Two 3-year-old boys found wandering Thursday in Brooklyn and in Queens have been reunited with their respective families, police say.

One of the boys was found near Livonia Avenue and Herzl Street in the Brownsville section of Brooklyn just after 1 a.m., police said. He was reunited with his family later in the day.

Authorities continue to question the relative and other family members in the case of the boy, who was found wearing a t-shirt, jeans and socks.

A law enforcement source tells NBC 4 New York the child's grandmother was watching him overnight so that his mother could go to a doctor's appointment in the morning. The grandmother didn't realize he was gone until she woke up Thursday morning, and when she couldn't find him, assumed his mother had returned and picked him up, the source said.

Then in Queens, a boy was found wandering in Flushing, near 163rd Street and Crocheron Avenue, police said.

Shortly after the 109th Precinct tweeted that it was trying to locate Zhang Chen's family, it said the boy was reunited with his family and "all is well."

It appears the boy left his house and began wandering while his mother was doing laundry and his father was asleep, police sources said.

We found 3 y/o Zhang Chen at 163 St & Crocheron Ave. We're trying to locate his family. Do you recognize him? pic.twitter.com/TJRv8WIZar — NYPD 109th Precinct (@NYPD109Pct) December 29, 2016

His parents couldn't report him missing right away because they speak only Mandarin and were trying to find an interpreter, the sources said. The parents are not expected to be charged.

The Top 16 News Stories of 2016