He claims his wife killed the baby and then committed suicide as they cuddled in bed.
Prosecutors said he was despondent over mounting debt and dissatisfied over his sex life.
During the brief sentencing hearing, Rachel's mother, Priscilla Matterazzo, called Entwistle's theory of a murder-suicide "low and despicable."
"Suffering does not begin to describe what we have been enduring without our beloved Rachel and Lillian," said Matterazzo, who wore a pink rose on her lapel in memory of her granddaughter. "I have lost two generations of my family."
Matterazzo asked that the life sentences be consecutive, to represent the two generations. But Middlesex District Court Judge Diane Kottmeyer said that would be only symbolic since there is no chance he'll be released, and imposed two concurrent life sentences.
Entwistle's family continued to support him.
"There is no way our innocent son Neil is guilty," his father, Clifford Entwistle, said before the sentencing. He refused comment afterward.
