Massachusetts Democratic Senate candidate Elizabeth Warren pushed back Thursday against nonstop questions about her claims to be part Native America by saying family member are off limits -- but not before another round or clarifying her personal history. Warren suggested incumbent GOP Sen. Scott Brown has gone too far in suggesting her parents mislead her into thinking her ancestors were Native Americans. "What kid asks their grandparents for legal documentation to go along with their family stories?," Warren asks in a letter to supporters. Scott Brown even questioned the honesty of my parents. Brown, who is seeking a second term, responded in part by saying: "My mom and dad have told me a lot of things, too, but they're not always true." The letter -- an apparent attempt to refocus voters on campaign issues -- followed a statement Wednesday night by the Warren Campaign in which the candidate publicly acknowledged for the first time that she told officials at Harvard University and the University of Pennsylvania that she had Native American heritage. The campaign said Warren gave that information to the schools only after she had been hired by them. Warren, who taught at Harvard Law School, has provided no documentation on Native American heritage, despite saying it is part of her family lore. She and Brown are locked in an expensive, essentially dead-even race that will help decide whether Republicans win control of the Senate. Warren also had a clarify comments made in a video tape discovered earlier this week. She claimed to be "first nursing mother to take a bar exam in the state of New Jersey," at the 2011 Chicago Humanities Festival in 2011, in a video posted on the group's website. Such a claim is practically impossible to prove or disprove. The Warren campaign responded by saying" "Elizabeth was making a point about the very serious challenges she faced as a working mom - from taking an all-day bar exam when she was still breast-feeding, to finding work as a lawyer that would accommodate a mom with two small children." In the letter, Warren said Brown and the rest of the Republican Party have for weeks "orchestrated an attack against my family, my job qualifications, and my character."