The two fighters meet at the Copper Box Arena in London on Saturday night.
The winners of the two fights could find each other facing off next time, and with so much on the line the fight has threatened to boil over.
Saunders (24-0, KOs 12) and Monroe Jr (21-2 KOs 6) clashed earlier in the week at a gym, where members of the American's entourage exchanged insults and headwear thefts.
Then when the pair met to weigh in ahead of the bout, Saunders' young son appeared to punch Monroe Jr in the groin and aim a kick at his shins before being pushed back by stewards.
He looked innocent enough, standing in front of promoter Frank Warren, even getting a pat on the head from Monroe Jnr.
Saunders, meanwhile, was completely impassive, nearly like he knew it was going to happen...
On Friday, a boxing weigh-in between WBO world champion Billy Joe Saunders and Willie Monroe Jr. went somewhere nobody expected.
But Billy Joe Saunders made no apologies for his son's behavior.
Saunders himself has now tweeted about the incident claiming that his son was simply defending himself as he's not used to being touched by strangers.