BOSTON  Gov. Deval Patrick today named Paul G. Kirk Jr., a former aide and longtime confidant of the late Senator Edward M. Kennedy, to Mr. Kennedy’s seat.

“He shares the sense of service that so distinguished Senator Kennedy,” Governor Patrick, a Democrat, said at a news conference in Boston. “The interests of the commonwealth have never been more vital or at stake in the Congress today.”

Mr. Kirk, a longtime friend of the Kennedy family and onetime special assistant to Senator Kennedy, is scheduled to take the oath of office on Friday and serve until a special election on Jan. 19; he has pledged not to run in the election. He said on Thursday that he would keep the late senator’s staff in place.

Mr. Kirk was the favorite of the late senator’s wife and two sons, as well as some officials in President Obama’s administration, according to people familiar with the matter. The president issued a statement after the appointment was announced.