EXCLUSIVE

Heavyweight champ Deontay Wilder is being sued by another boxer over a post-fight melee back in February in which Wilder allegedly screamed out, "F*ck your kids."

The man behind the suit is fellow heavyweight fighter Dominic Breazeale -- who fought on the same card as Wilder in Birmingham, Alabama on Feb. 25.

After the boxing matches, Wilder and Breazeale got into it in the lobby of the Westin Hotel -- a violent incident Breazeale claims was started by Wilder and his camp.

In his suit, Breazeale says he was with his wife and kids (ages 5 and 8) when Deontay and his brother, Marcellus, attacked him out of nowhere ... throwing punches, spitting and cussing like crazy people.

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Breazeale says his wife begged the Wilders to stop fighting in front of the children to which Deontay replied, "F*ck your kids."

Breazeale says not only was he assaulted and injured in the brawl -- but his kids are emotionally scarred by the incident.

Breazeale says his younger child is afraid for his father's life and repeatedly asked if Deontay and Marcellus are going to kill him.