Ashlee Simpson and Pete Wentz are expected to tie the knot soon!

ASHLEE SIMPSON's wedding guests -- including older sis' JESSICA with TONY ROMO -- began arriving at patriarch JOE SIMPSON's L.A. home around noon on Saturday, OK! magazine reports.

Tony and Jess arrived together in 'The Dukes of Hazzard' star's Range Rover, while groom PETE WENTZ cruised up in a limo, according to the mag. NICOLE RICHIE and JOEL MADDEN -- who reportedly took part in Friday night's wedding rehearsal dinner -- are also expected at the nuptials, as are Pete's FALL OUT BOY bandmates.

The wedding hour ticks ever closer, so keep checking back here for more details.