The family of the Irish immigrant who was fatally punched in a bar fight on Thanksgiving faced down the alleged killer for the first time in Queens court on the same day as the victim’s 22nd birthday.

Steven O’Brien, 25, is accused of landing one punch to Gaelic football player John “Danny” McGee when the pair were arguing at 3:45 a.m. outside Sunnyside bar The Gaslight, knocking him back and killing him when his head hit the pavement.

McGee’s uncle, Tim Murphy — who came to court with about a dozen supporters, including some of McGee’s co-workers — said he saw O’Brien for the first time Friday, adding that “it was very difficult.”

Murphy’s wife, Denise, said it was especially hard because “Today would have been his 22nd birthday.”

Murphy said, “Christmas was difficult, Thanksgiving was difficult because that was the day it happened and it will be for the rest of our lives.”

“We want this man to get punished as much as he can … he killed somebody,” Murphy added.

O’Brien and McGee had met mutual friends at the bar, and a bartender told cops at the time that both were highly intoxicated when the argument broke out.

The alleged assailant “Punched him one time in the right side of the head, causing the victim to fall to the ground,” according to a criminal complaint.

After the assault, O’Brien — also originally from Ireland — fled, cops said.

McGee was originally from Drumlish in County Longford, where he played Gaelic football and was a member of the Father Manning Gaels. His immediate family still lives in Ireland, Murphy said.

O’Brien — who appeared briefly in Queens criminal court — is charged with one count of second-degree assault and faces up to one year in jail if convicted.

His lawyer, Matthew Gartenberg, said, “Mr. O’Brien is presumed innocent and we are going to keep fighting these charges.”

He is due back in court on Feb. 21.