11:18 AM PT -- Sources with direct knowledge tell TMZ Sports ... James Anthony Hill Jr. is Jamahal Hill's brother.

Former UFC light heavyweight champion Jamahal Hill was arrested in Michigan for domestic violence earlier this week ... TMZ Sports has learned.

According to records, the fighter was booked at a Kent County jail on Monday at around 1 AM ... and released later that evening, at 7:35 PM. That same day, prosecutors formally charged the 32-year-old with one count of misdemeanor aggravated domestic violence.

In court documents we obtained, officials allege Hill assaulted James Anthony Hill Jr., inflicting "serious or aggravated injury upon him."

It's unclear if the two Hills are related, though officials said in the docs James is "a resident or former resident" of Jamahal's household.

Further details surrounding the allegations were not made immediately available. Hill is due in court in January for a hearing on the matter.

We've reached out to Jamahal's reps for comment, but so far, no word back.

Jamahal just recently earned his light heavyweight crown in January with a win over Glover Teixeira at UFC 283 -- though he relinquished the title in July after he ruptured his Achilles while playing basketball.

Once healed, Jamahal is expected to get another crack at regaining his belt in a fight with the division's current champ, Alex Pereira.