Police didn't release the names of the couple, but said they were asleep in their quiet neighborhood just after midnight Wednesday when they were pummeled by three shadowy figures, one of whom was carrying a machete, The Washington Post reported.
After the beating became bloody, the invaders left. The homeowner called for help out the window, and someone heard him and dialed 911.
Police said the couple's 23-year-old daughter may have complained to some friends after a fight with her parents, but they said they don't believe she knew her friends would take matters into their own hands.
Two Herndon, Va., men were arrested and charged with malicious wounding: Rolando Miranda-Perez, 18, and Noe Eli Alvarado-Chopin, 22. Both were arrested Friday and are being held in the Fairfax jail without bond.
Police were still looking for the third suspect, Raul Antonio Aleman Argueta, 20, also of Herndon.