The 47-year-old singer shared a picture Tuesday of her daughter, 9-year-old Emme, spending time with Rodriguez's elder daughter, 12-year-old Natasha, on their trip to the Dominican Republic.
"Tashi and lulu..." she captioned the photo for her 63.4 million Instagram followers. Fans immediately gushed about the girls in the comments, with many proclaiming the pair look like sisters or twins.
"The girls look like sisters. Maybe future stepsisters," one person wrote.
"So adorable....ummm is it me or dont they look like twins?" another said.
Lopez shares Emme and 9-year-old son Max with ex-husband Marc Anthony, while Rodriguez is dad to Natasha and 8-year-old Ella with ex-wife Cynthia Scurtis. The new couple and their children spent Easter weekend as a family.
"Jen and Alex woke up early and had Easter baskets outside lined up on the patio waiting for the kids," a source told E! News. "They had family and friends over for an egg hunt on the sprawling lawn of [the resort]."
"The kids got along great and had a fun time," the insider added. "[They have] really bonded and become good friends. A-Rod's older daughter, Natasha, is like a big sister to J. Lo's twins."
Lopez and Anthony performed a sold-out show Saturday at Altos de Chavón Amphitheater. The friendly exes were later spotted dancing with Rodriguez, who was first linked to Lopez in March.