Twisted killer Lyle Menendez is keeping a shocking secret from his new 21-year-old British student lover. Knewz.com can reveal the two-timing jailbird, a serial cheater who first betrayed wife Rebecca Sneed a dozen years ago, became the " prison wife" of a convict by the name of Chino. Convicted with his brother Erik of the bloody slaughter of their parents 23 years ago, Lyle had proclaimed his love to Sneed, who he wed in 2003, in phone calls every morning and during her visits to prison. But