Sanders can recall only one Wisconsinite who joined Manson's traveling acid test. "I never heard of any other woman associated with the family besides Mary Brunner, who was pregnant at that point in time," he says. (Brunner went to prison for taking part in an armed holdup in 1971; she was released a few years later and went into seclusion. Her son—fathered by Manson—surfaced in media reports in the early nineties as Michael Brunner, but he, too, has slipped from sight.) "So this would've been a rival to Mother Mary," Sanders goes on. "I think I would've heard about it, but you never know. Short of paying for DNA, I don't see how you're going to confirm it." On the other hand, we're talking about the late sixties. Roberts says that his mother fell under Manson's spell for only a short time before fleeing back to the Midwest. Manson did indeed spend the Summer of Love darting in and out of San Francisco, and he was notoriously promiscuous during his Haight-Ashbury phase. As Sanders writes in The Family, "if one calculates, with data supplied by Manson intimates, an average of three orgasms a day for a total of something like three thousand fornications in two and a half years, one would expect a greater number of pregnancies."

With a cast of unreliable narrators, it's probably impossible to pin down the whole truth. If Roberts' biological mother truly didn't know that Manson had fathered her baby, then how did he learn of the name Lawrence Alexander? Either way, there's no denying that Matthew Roberts is an ambitious fellow. He wants to develop a "son of Manson" reality show with a production company in Orlando and counts among his close advisers Vicky Hamilton, a savvy West Coast music-biz fixture who helped break bands like Guns N' Roses and Poison. A few years ago Roberts auditioned for Slash in a bid to become the singer for Velvet Revolver. "I've been in seclusion for long enough," he says. "Superstardom would be kind of cool."

Which might lead you to wonder: Could the whole saga be a stunt to draw attention to his music? "I've been accused of trying to promote my band," Roberts concedes. "But I've never made one phone call. People call me." Still, he understands why some are skeptical. He, too, doubted the story early on. "I kind of kept it to myself, because I really didn't expect anyone to believe it," he says. "I mean, it just seems so ridiculous."

Lately Roberts has been spending a lot of time in Chicago with his adoptive family; they've been struggling with a raft of illnesses. As tight-lipped midwesterners, they prefer to ignore the Manson tale altogether. "They just don't talk," he says. "Their whole thing is you put on a good face." Roberts is no longer in touch with his biological mother—her letters, he says, became too demented and hostile. While he may have inherited a rather twisted perspective on parenting, Roberts wouldn't mind becoming a father someday. "I may have a kid out there," he admits. "And that's weird. I would love to know the kid, but it was a one-day affair. She showed me the ultrasound, said it might be mine, and I never saw her again. My kid will probably be a Republican or something, and I'll have to deal with it."