Kyrsten Sinema’s boyfriend, Matthew Ammel, is involved in a bitter court battle with his estranged wife — and the ex claims Matthew abused narcotics and psychedelics … TMZ has learned.

Matthew’s estranged wife, Heather Ammel, filed court docs in March 2025 seeking custody of their three kids and child support.

In seeking primary custody of the kids, she claims Matthew has a history of “uncontrolled bouts of anger” … adding he oftentimes expresses his anger by punching the wall of their home and “breaking and destroying furniture and screaming at” Heather “in a fit of rage.”

Heather said she wed Matthew on October 23, 2010, and separated on November 1, 2024. They share three children: Clara, Isla and James.

She alleges Matthew has a history of substance abuse — including marijuana, narcotics, alcohol and psychedelics — and she says “he continues to abuse these substances.” (Kyrsten and Matthew have spoken out in favor of psychedelics and argued for more research on the matter.)

Heather says Matthew “regularly travels out of the country to obtain and consume illegal substances” and says she worries that he leaves the substances in areas accessible to the kids. She also claims she feared he was going to flee the country with their kids.

Heather says Matthew demeaned and degraded her in front of their kids … calling her a “nasty cu*t” and “a f***ing dumb bitch.”

She claims Matthew moved out of their home in November 2024, but says he often shows up uninvited.

Matthew denies all of Heather’s allegations of drug use and denies he degraded her.