Kerry, D-Mass., Friday was nominated to replace Secretary of State Hillary Clinton. He is expected to win easy approval.
Kennedy, son of the late Sen. Edward Kennedy, has been encouraged by friends and Democratic Party leaders to run for the open seat, the family friend told the Boston Globe.
"He is listening to everyone, but he is not going to make a decision unless there is an open seat," said the friend.
A poll this week by WBUR-FM, Boston, found if Republican Sen. Scott Brown decides to run, he was favored to win against several Democrat candidates but Kennedy was not among those whose names were polled.
"What we have in Massachusetts with some of the names being discussed is that they are not well known, they have a statewide name ID problem," said a Massachusetts Democratic operative, who is not associated with the Kennedys. "Ted Kennedy Jr. does not have that problem."