The service will be held at 1 p.m. at the Church of Jesus Christ of Latter-day Saints Stake Center in Puyallup, south of Seattle.
The boys, 7-year-old Charlie and 5-year-old Braden were killed by their father, Josh Powell, on Sunday in a fire at his home in nearby Graham, Wash.
Powell was a person of interest in the disappearance of his wife two years ago, and he had been denied custody of his boys, who had been living with Susan Powell's parents recently.
Steve Downing, an attorney for Susan Powell's parents, said the public is welcome at the service. The address is 13420 94th Ave. East in Puyallup.
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