Prince Harry and Meghan Markle are having a moment deep in the heart of Texas -- they made an unannounced stop to see the family of Irma Garcia ... a teacher killed during the Uvalde school shooting.

The Sussexes headed to Uvalde Saturday to spend some QT with Irma's family. You might recall, her story was even more tragic, because her husband Joe died 2 days after the mass shooting from a heart attack.

The Garcias were delighted by the surprise visit, with her nephew John Martinez writing on X: "Meghan Markle and Prince Harry came to my house! They're such a beautiful couple and I'm so blessed - so glad they came to check up on the family!"

Martinez also gushed about how loving and supportive H&M were to his cousins ... and also shared a clip of the pair singing "Happy Birthday" to his mom.

As you can see, Harry and Meghan also posed for snaps and chatted with the Garcias ... virtually becoming part of the family for the day.

Meghan first connected with the Garcias a few days after the tragic 2022 shooting ... while she was in Uvalde to honor the slain teachers and students.

MM was pictured visiting outside the nearby Uvalde County Courthouse at the time ... leaving a bouquet of white roses at a makeshift memorial.

Weeks later, she reached out to Irma's sister to check on the family's wellbeing, especially the 4 children who lost both their mom and dad under heart-wrenching circumstances.