Patrick Lyttle, who was allegedly knocked unconscious by his brother in Australia during an argument, has come out of a coma.
The 31-year-old is said to be "conscious and sitting up".
David Faktor, a spokesman for the hospital where Mr Lyttle is being treated confirmed that he is in a stable condition and will remain in the intensive care unit for a number of days.
He also confirmed that he was conscious and has been taken off life support.
Patrick had been travelling in Australia since June and met with his father Oliver and older brother Barry Lyttle (33) just four days before the incident.
An argument between the two brothers, from Ballycastle, Co Antrim, is alleged to have occurred in the King's Cross area of Sydney last weekend.
On Saturday, Barry was charged with recklessly causing grievous bodily harm after allegedly assaulting his younger brother.
Police have alleged that Barry hit his brother in the face, causing him to fall and hit his head on concrete.
Barry appeared before the local court on Tuesday and was granted bail.
He sobbed during his court appearance.
Barry has been a constant presence at his brother's bedside since then.
After his appearance, the brothers' father Oliver said his sons had loved each other since they were young and this was a tragic accident.
Police have ruled out alcohol as a factor in the incident.
After the alleged assault, Patrick was rushed to St Vincent's Hospital with critical head injuries.
He had been on life support in the hospital, but this morning he woke up and was sitting up in bed.
The brothers' dad Oliver (74) had spoken briefly outside the court hearing, expressing his gratitude for the outpouring of sympathy, and saying that the brothers were extremely close.
Friends had revealed that Patrick had been backpacking in Australia touring the country for about five months, before his brother and father flew to Sydney for Christmas.
The incident happened outside a nightclub at 3am on January 3 local time.
Oliver had gone home after dinner, but the two brothers continued on to a club.
A local newspaper described Patrick regaining consciousness as a "remarkable turn-around".
Meanwhile, if convicted, Barry will not face Australia's controversial minimum four year sentence for a "one-punch" assault as the amount of alcohol in his system was well below the threshold.
Superintendent Michael Fitzgerald of the New South Wales Police, has previously said that alcohol was not a factor in the alleged assault as Barry's blood alcohol reading was in the low range.
Meanwhile, Barry has uploaded a photo to Facebook of the brother and their dad in Sydney on New Year's Eve.
Barry is due back in court on January 20.