Joseph Kennedy III is formally jumping into the race for the Massachusetts congressional seat now held by retiring U.S. Rep. Barney Frank.
A member of the campaign who requested anonymity so as not to preempt the candidate's announcement tells The Associated Press the Democrat is expected to make the announcement Thursday.
Kennedy recently moved from Cambridge to Brookline, part of the state's newly redrawn 4th Congressional District.
Kennedy is the son of former U.S. Rep. Joseph Kennedy II and a grandson of the late Robert F. Kennedy. The family has deep ties to the Boston suburb.
Kennedy announced last month he was forming an exploratory committee to look at a possible run for the seat.
At least two other Democrats and two Republicans are considering runs.
The last Kennedy on Capitol Hill was Rep. Patrick Kennedy, who represented Rhode Island for eight terms until 2010 and is the son of the late Sen. Edward M. Kennedy. After Patrick Kennedy vacated his office, it was the first time in 64 years that Kennedy family member was not in the White House, U.S. Senate or House.