Jessica VS Ashlee Simpson : It’s War!

“There’s certainly a sibling rivalry between them,� a source close to the two tells Star. The trouble began, says another insider when Jess’s boyfriend, John Mayer, pointed to a glamorous magazine photo and asked Jess, “How old is this picture of you?� Turns out that was a shot of Ashlee! “Jessica read John the riot act,� says our source.

“He definitely touched a nerve.�

Her sensitivity on the subject seems to be the direct result of Ashlee’s emergence as a sex kitten, a role once owned by Jessica. That Ashlee has become the hot blonde – a transformation that came courtesy of a surgeon’s knife, a bottle of peroxide and dramatic weight loss- is troubling to Jessica, who has morphed into a buxom and sometimes frumpy brunette due to a dye job and about 20 extra pounds.

“Jessica hears the catty talk about how Ashlee looks like her- from two years ago,� says the source. “It totally bothers her.�

Meanwhile, Jessica Simpson has admitted that she is naturally brunette.

The singer, who was recently spotted sporting a dark haired look instead of her trademark blonde hair, revealed to Us Weekly that though she was "really blond" as a child, her hair changed color as she grew older.

"People don't know that about me. I was really blond as a kid, but then I just started getting darker and darker," Us Weekly quoted her, as saying.

"I've really become comfortable in who I am and my skin and just feeling beautiful five pounds heavier, five pounds smaller," Simpson said.