The ex-mistress of Baron de Rothschild and her illegitimate socialite daughter are locked in a bitter $6 million legal battle with their luxury condo over their family trees, according to a lawsuit filed Friday. The mother-and-daughter duo bought two penthouse apartments for $12.9 million in 2006 in upscale Turtle Bay on East 53rd St., and then poured in another $5 million to combine them, said the lawsuit filed in Manhattan Supreme Court.     Read more……….