Sen. Elizabeth Warren sought Sunday to bolster her shaky claims of Cherokee ancestry with the story of how her racist grandparents drove her parents to elope. But Cherokee genealogist Twila Barnes says that account has its own credibility issues. Ms. Barnes, who said her research into Ms. Warren's family found "no evidence" of Native American ancestry, has challenged key elements of the senator's tale of how her parents, Pauline Reed and Donald Herring, defied his parents by running off to marry. [Snip] After Ms. Warren said in the Globe that her mother told her "nobody came to her wedding at...