Kyle Massey -- the former Disney Channel star -- is tying the knot ... and, his future wife is related to '80s Hollywood royalty.

Hana Giraldo -- the daughter of legendary rock singer Pat Benatar -- posted a photo to her Instagram Friday ... sharing a pic of the two beaming, with Hana extending her left ring finger to the sky to show off her new ring.

It's a massive rock, and Hana gives fans a close-up look at it in another photo ... adding "IM ENGAGED