William Dunlop outshone brother Michael by winning four races at the Skerries 100 meeting near Dublin on Saturday.
The Ballymoney man, who rides for the Wilson Craig Honda team, took the chequered flag in the Supertsport, 125cc, 250 and the grand final races.
Dubliner Derek Shiels won the first Open race ahead of John Burrows with William Dunlop beating brother Michael to third place.
Michael was runner-up in the Supersport with Saintfield's Davy Morgan in third.
Wayne Kennedy was second behind William Dunlop in the 125s with Nigel Moore in third.
William Dunlop led the Grand Final race from start to finish lead to beat Michael Dunlop, who set a new lap record, and Davy Morgan was third.
John Burrows won the Super Twins race.