Ariana Grande Boyfriend Ethan Slater's Estranged Wife Feels He ...

Ariana Grande and Ethan Slater's romance came as a surprise to the Broadway actor's now-estranged wife who feels he abandoned his family ... TMZ has learned.

Sources close to Lilly Jay -- who married Slater back in 2018 -- tell us she's devastated her family's been torn apart. She's also upset their young son, who was born in August 2022, won't have both his mom and dad around constantly, now that they've split.

Our sources say Lilly and Ethan aren't on good terms now that the Ariana relationship is full steam ahead.

We're also told, for her part, Lilly feels like he's completely turned his back on his family.

What's more, we're told Ariana actually used to hang out with both Ethan and Lilly while they were still a happily married couple, and she even liked his Instagram tribute to Lilly on Mother's Day this year. Remember, we're told Ariana and Ethan's romantic relationship started several months ago.

The whole thing has left Lilly feeling betrayed and heartbroken ... according to our sources.

Additional sources close to the situation tell us, "It's understandable that emotions are high and it's hard seeing your ex move on, especially in such a public way, and her friends are trying to protect her. But Ari and Ethan are just trying to lay low and be respectful of their exes as they pursue this new relationship."

TMZ broke the story ... Ariana and Ethan first met on the set of "Wicked" and their relationship grew from there. Sources close to them have maintained both Ariana and Ethan were split from their spouses -- Dalton Gomez and Lilly -- when they got together.

Sources tell us while they haven't yet filed divorce docs, there's definitely one on the horizon for Ariana and Dalton.

As for Lilly and Ethan ... it doesn't appear either has filed yet, but it sounds like things are beyond repair.