Anne Heche's 24-Year-Old Son Homer Laffoon Accused of Being a 'Deadbeat Dad' to Toddler Son

Homer Laffoon isn't just the son of late actress Anne Heche ... he's also a "deadbeat dad," at least according to his baby mama.

Jessica Lamberto told Page Six that Homer, 24, has "never, ever, ever" reached out to check in on their almost-3-year-old son, Rocco -- who she says is nonverbal, has been diagnosed with autism, and has global developmental delay.

The 42-year-old mother told the outlet ... "I'm still in shock with Rocco being diagnosed, even though I already knew. As a mother, I knew ... But hearing it confirmed just shattered my heart."

According to Jessica, Rocco also had an MRI recently ... and she's still waiting for the results.

The self-described "single mom" says she drives Rocco to physical, occupational, speech and behavioral therapy appointments every day ... but says his 24-year-old dad is zero help.

She claims Homer is a "s***ty person" who "failed" his son, noting she'll "never forgive" him for allegedly going AWOL.

In fact, Page Six reports the Riverside County Department of Child Support Services has an open child support case against Homer ... and as of August, he still hadn't been served.

DCSS told Jessica ... "At this time, we may not have enough information to identify or locate the parent ordered to pay support."

She told Page Six that she and Homer had been friends ... and she found out she was pregnant with his child 6 months after his mom's tragic death.

Jessica claims Homer wasn't sure how involved he wanted to be with their child, and previously told the Daily Mail that he was a no-show at the hospital when she was giving birth and didn't sign the birth certificate.

She claims Homer didn't even meet Rocco until the baby was 2 months old ... and hasn't seen him since last May.