Justin & Jessica: Party Into the Wee Hours

Timberlake and Biel lock lips all night long at a soiree celebrating his well-received William Rast fashion line

Justin Timberlake and Jessica Biel continue to make a very fashionable couple—who also persist in proving the naysayers wrong.

Not only was Biel at Timberlake and Trace Ayala's William Rast fashion show in New York City yesterday, but she was also sitting next to his parents, Lynn and Paul Harless.

And the good times didn't stop there...

Timberlake and Ayala hosted a star-studded afterparty at Hudson Terrace, where the "SexyBack" singer and his Valentine's Day starlet locked lips throughout the four-hour soiree, according to a source.

The two shared a table, which was never without a bottle of Timberlake's 901 tequila. "Justin performed one song, causing the crowd, including Jessica, to go wild," the source said. "The stayed until 2:30 a.m."

Also at the party was our favorite new Calvin Klein underwear model, Kellan Lutz, plus Ryan Phillippe, Saturday Night Live's Abby Elliot and former American Idol wannabe/Broadway star Constantine Maroulis with girlfriend Tinsley Mortimer.

Meanwhile, Biel is getting some high praise from Timberlake's mom.

"She's amazing," Lynn told People magazine. "She's so down-to-earth and her family is great."

While Lynn said she was anxious to become a grandmother, she stopped short of saying Biel was the one. "You should ask him. I've thought that before," Lynn said. "They're young. They have plenty of time."