Northern Ireland's most senior judge Sir Declan Morgan increased Patrick and Paul Somers' prison terms from 12 months to two-and-a-half years.
In 2014, the pair had pleaded guilty to wounding a man with intent to cause grievous bodily harm.
The man needed plastic surgery to an ear injury inflicted during the attack.
Shane Gallagher was beaten and stamped on by the brothers with a pool cue at the Roundhouse Bar in Enniskillen in October 2013.
Patrick Somers, 21, from Hillview Park, and Paul Somers, 20, from Drumbeg, were originally handed three-and-a-half year sentences, of which a year was to be spent in jail.
However, that was appealed by the Director of Public Prosecutions Barra McGrory.
On Friday, Sir Declan ruled that the case involved high culpability and premeditation.
He said: "There is a long line of authority from this court dealing with the problem of wanton violence by young males, often after the consumption of large amounts of alcohol."
The court heard how the brothers had returned to the bar based on a false allegation that their mother had been assaulted.
CCTV footage showed Patrick Somers walk straight up to the victim, knock him to the ground and punch him up to six times before stamping on his head.
His brother Paul had armed himself with a pool cue which he used to strike Mr Gallagher about seven times.
He also lifted bar stools and tried to hit the victim, who had been rendered unconscious at some stage in the attack.
Mr Gallagher sustained a deep cut to his ear lobe, as well as cuts to his eyelid and head, and heavy bruising.
He said that he was lucky not to have lost his ear or been killed in the assault.
Sir Declan said the sentencing range for such attacks was designed to act as both a deterrent and to protect the community.
He ordered the men to serve five years, half of which will be served in jail and the remainder on licence.
Two brothers from Enniskillen received unduly lenient sentences for beating a man unconscious in a bar in 2013, the Lord Chief Justice has ruled.