Jess Kent Thomas and Kent David Thomas were each charged with aggravated burglary and assault after breaking in to another family member's Youngtown unit and bashing her partner on Christmas eve in 2017.

Kent, 49, and his 28-year-old son appeared unrepresented on the first day of their trial. Not guilty pleas were entered and a jury was empanelled, but the two men changed those pleas to guilty shortly after the morning tea break.

Justice Robert Pearce dismissed the jury.

Crown prosecutor John Ransom told the court there was a verbal altercation at a Thomas family Christmas function preceding the Youngtown incident.

Hours later, Kent and Jess went to the unit and kicked the front door in about 10.15pm.

Kent walked straight to the bedroom of Colin Corsa, who was asleep moments before the incident, and punched him several times.

Mr Corsa was bitten on the left side of his chest by Kent. While the victim fought with Kent, he was punched to the kidneys, head and back by Jess.

Mr Corsa poked Kent in the eye and started pushing Jess away from the bedroom, toward the front door.

Jess threw a number of punches, as well as biting the middle finger and thumb of Mr Corsa's left hand.

During the fight, Mr Corsa flipped over a banister outside his house, landing on a lawn mower in the front yard.

He stayed on the ground for about 10 seconds because he was winded, before hiding behind a lemon tree in the yard.

Mr Corsa was treated at the Launceston General Hospital for multiple superficial abrasions, bite marks and stitches on his toe.

During sentencing mitigation, Jess told the court he met Mr Corsa about 15 years ago when his aunt called him for help because her partner was abusing her.

"I do fear for my aunty's safety," he said.

Kent told the court he and Jess regretted what they did.

"Colin has been a pretty bad person in our family for a long time," Kent said.

In a victim impact statement read to the court by Mr Ransom, Mr Corsa said the incident left him anxious, angry and feeling unsafe.

Justice Pearce ordered Jess and Kent undergo a pre-sentence report. The two men were bailed to appear for sentence on September 16.