Mercede Johnston, Levi Johnston's sister, is revealing all -- literally -- for an upcoming Playboy interview and photo shoot.

There is clearly no love lost between the Palin and Johnston clans, and if Mercede's anecdotes are to be believed, the Palin family is far from picture-perfect.

The 18-year old claimed that Track Palin was forced into military service so as not to detract from his mother's vice presidential campaigning in 2008.

"He didn't choose to go into the Army; he went there because his mom made him, to get him out of the way so when she was at the convention they wouldn't know he does drugs and would think he was a patriot."

Johnston said Track Palin did Oxycontin and cocaine. (Johnston's mother is currently serving a three-year house arrest sentence for selling Oxycontin.)

The soon-to-be centerfold also put in her two cents about Sarah Palin's political future, claiming she would have a "mental breakdown" if she were elected president, pointing to the fact that Palin did not finish her term as Alaskan governor.

Johnston also insisted that Palin is far from well-liked by Alaskans, claiming that 70 percent of residents in her hometown of Wasilla  "can't stand" her.

The overprotective sister of Levi Johnston did not spare the mother of her nephew. According to Mercede, Bristol Palin sent a text message to Levi during her pregnancy that read, "Ever since the moment I found out I was pregnant, I prayed to God you weren't the father."

She added that her brother did not like Bristol to drink, as it made her "more promiscuous."

Mercede's photos and interview will appear in the September issue of Playboy.