Pete Wentz and Ashlee Simpson

It's no secret that Joe Simpson has quite the thumb on his two star-studded daughters. It seems he is even reigning over Ashlee's “big day.”

The youngest Simpson sister is reportedly set to tie-the-knot with Fallout Boy frontman Pete Wentz on Saturday evening at Joe's mansion within a gated community in Encino, Calif. The musicians started dating in the fall of 2006 and announced their engagement on April 9, fueling rumors that Simpson is "expecting."

An inside source told Tarts that plans were to keep the ceremony pretty "small and intimate" and that it was to be attended only by close family and friends.

On Saturday morning Pop Tarts observed several large trucks and people going coming and going and at the residence.

Jessica Simpson also apparently hosted a rehearsal dinner for her 23-year-old sister in her Beverly Hills home Friday evening.

Speaking of Jessica...

The Internet has been running rampant this week with reports that Jessica Simpson has split from Dallas Cowboys quarterback Tony Romo.

While reps for the Texan twosome have been busy denying the split, a source close to the Romo camp told Pop Tarts that their relationship has hit a "rough patch" but might not be totally over just yet.

After all, he apparently already had plans to get down on one knee for the songstress, and just recently she referred to him as her "future husband" in Glamour magazine.

According to our inside source, Tony was organizing an "intimate dinner for friends and family" to take place in Texas within the next few weeks in anticipation of announcing his engagement to the eldest Simpson sister.

"Every couple has their problems; we're hoping that they'll have a break and work it all out," the source said. Calls to Simpson's rep were not returned.

So while Romo’s initial matrimonial plans seem to have been put on the back-burner, Jess and Tony are apparently still "talking."

So what's the problem?

Romo, 28, reportedly still has a roommate and loves his freedom, while Jess, 27, already has been married and divorced and has made it clear she wants to be a mom soon.

"Jessica has made no secret of the fact she wants to get married, and with all the Ashlee wedding talk and Jess’ dad’s involvement, Tony was obviously feeling it," another source said. "I wouldn’t be surprised if he just couldn’t go through with the proposal and that’s what’s caused the break."

Ashlee Simpson and Pete Wentz Enjoy Pre-Wedding Parties

Acknowledging a time-honored tradition, bride-to-be Ashlee Simpson celebrated the impending end of her single status with an all girl get together on May 15, 2008. According to E! online, the "Little Miss Obsessive" singer and her party posse soon moved from the sedate setting of her parent's residence in order to check out the pleasure treasures sold at Kiki de Montparnasse, a Beverly Hills boutique brimming with such naughty notions as Amour peek-a-boo lingerie and lace beaded blindfolds.

Pete Wentz also said bye bye to bachelorhood, bonding with his buddies and soon-to-be father-in-law during a celebratory dinner at Mr. Chow. A landmark restaurant among luminaries, Mr. Chow is the eponymous eatery of Michael Chow, an actor recognizable to movie buffs from his roles in You Only Live Twice, Rush Hour and Lethal Weapon 4.

From hosting the first Academy Awards ceremony to supposedly harboring the restless ghost of cinematic legend Montgomery Clift, the Roosevelt Hotel is the architectural heart of Hollywood. The soon-to-wed couple and their respective friends and family members ended their late night fete at the hotel's Marilyn Monroe suite, where the lovebirds could look down on the waters of the same palm-lined pool where the silver screen siren posed for her first ad.

Ashlee and Pete Rehearse at Jessica's House

Wedding weekend got even more officially under way tonight.

A day after Ashlee Simpson celebrated her bachelorettehood with family—including her future mother-in-law—and gal-pals, Jessica Simpson hosted a private rehearsal dinner for her little sister and Pete Wentz at her Beverly Hills home.

Red-vested valet attendants greeted the friends and family who were invited to the intimate affair, held in the elder Simpson sib's backyard. Guests were also spotted mingling on the front terrace.

Candlelit tables and twinkling white lights strung through the trees helped set the mood.

A source tells E! News that Ashlee and Pete arrived via limo at about 7:45 p.m., while a team of security guards held court on the street outside.

There's no confirmation yet that Jessica's boyfriend, Tony Romo, was there, but the NFL star is reportedly planning to accompany the singer to the Simpson-Wentz wedding tomorrow night. The apparently cohesive couple were spotted having lunch at the celeb-frequented Katsuya in Hollywood earlier today.