The incident happened around 1:30 p.m. at the intersection of Lancaster and Bryn Mawr Avenues near the Ludington Library.
According to police, a woman was crossing Lancaster Avenue with her 5-year-old twins when they were struck by a black pickup truck turning off north Bryn Mawr Avenue onto westbound Lancaster Avenue.
The truck did not stop.
All three victims were taken by ambulance to Bryn Mawr Hospital. One of the children was taken to Nemours/Alfred I. duPont Hospital for Children in Wilmington, Delaware overnight Thursday having sustained a head injury. That child was listed in stable condition Friday morning.
The striking vehicle is described as a full-sized black pickup truck similar to a Ford F-150.
Anyone with information is urged to contact Lower Merion Police at (610) 649-1000 or the Lower Merion Police Traffic Safety Unit at (610) 645-6260.