The two adults were shot, and the boys - 13-year-old Manuel, 10-year-old Adam and 6-year-old Ryan - were stabbed multiple times.
Gilleo was given the maximum sentences in Dutchess County Court Tuesday on each of 41 charges, including 20 counts of first-degree murder and 11 counts of second-degree murder.
Serrano was convicted in December and will be sentenced next week.