Maurice Hawell, 30, his brother Marius Hawell, 22, and Andrew David, 30, were hit with the verdicts on Monday after an almost four-week-long trial in Sydney's Downing Centre District Court.
The trio stayed with seven other men at an Airbnb in Newcastle over a weekend in February 2022 ahead of groom Maurice Hawell's wedding.
Jurors heard the men met three teenage women at a nearby pub and separately invited them back to the unit.
After having consensual sex, two 18-year-old victims went to retrieve their phones from a darkened bedroom where they were pushed onto the bed, stripped and "swarmed" by naked men, crown prosecutor Craig Evans previously said.
Describing exactly who performed which sexual act was impossible because the room was dark, but prosecutors alleged the three men were engaged in a joint criminal agreement to rape and sexually touch the women.
On the following night, a 19-year-old said she entered the apartment on the pretext of drinks but was raped by Maurice Hawell and David, who took turns swapping sexual positions.
Marius Hawell came into the room and watched, Mr Evans told the court.
On Monday after eight-and-a-half hours of deliberations, the jury reached unanimous verdicts on nine of the 11 counts against the men.
All three were found guilty of multiple counts of aggravated sexual assault in company relating to all three women and of aggravated sexual touching and the attempted aggravated sexual assault of one woman.
The jury will continue their deliberations for the two remaining charges of attempted sexual touching against Maurice Hawell and aggravated sexual assault in company relating to all three men.
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