Dorothy McGuire Williamson, who teamed with sisters Christine and Phyllis for a string of hits in the 1950s and ’60s as the popular McGuire Sisters singing group, died Friday at her son’s home in the Phoenix suburb of Paradise Valley. She was 84 and had Parkinson’s disease and age-related dementia.(Actress Dorothy McGuire died in 2001.) The McGuire Sisters earned six gold records for hits including 1954′s “Sincerely” and 1957′s “Sugartime.” The sisters were known for their sweet harmonies and identical outfits and hairdos. They began singing together as children at their mother’s Ohio church and then performed at weddings and church revivals. They got their big break in 1952 on “Arthur Godfrey’s Talent Scouts” show, where they performed for seven years. The group made numerous other appearances on television and toured into the late 1960s, making a last performance together on “The Ed Sullivan Show” in 1968. Dorothy and sister Christine stepped out of the spotlight while Phyllis pursued a solo career, and the trio reunited in the mid-1980s and began doing nightclub and Las Vegas performances again. The sisters last performed together in the mid-2000s and are featured on a 2004 PBS show called “Magic Moments — Best of ’50s Pop.” The group performed for five presidents. They were inducted into the National Broadcasting Hall of Fame in 1994 and the Vocal Group Hall of Fame in 2001. Christine and Phyllis, 86 and 81 respectively, live in Las Vegas. McGuire is survived by her husband of 53 years, Lowell Williamson, a wealthy oilman; two sons; two step-children; and nine grandchildren. A memorial service is set for Sept. 15 at Valley Presbyterian Church in Paradise Valley, Ariz.