Julia Roberts has allegedly refused to attend her sister's wedding.The 'Runaway Bride' star, 45, doesn't approve of her younger half-sister Nancy Motes' fiance John Dilbeck and plans to boycott their upcoming nuptials because she is worried she might have to foot the bill.A source told The National Enquirer: "Julia doesn't think much of Nancy's husband-to-be. She's convinced he's sponging off Nancy, who doesn't have much money in the first place."Now, Julia won't go to her wedding because she's worried Nancy will try to tap her for more money."Nancy, who shares the same mother as Julia, is said to work as a production assistant on 'Glee' because her Oscar-winning sister got her the job.Julia married her own husband Danny Moder on July 4, 2004 at her 82-acre ranch in Taos, New Mexico. The wedding was a surprise to the 60 guests, who were invited to an Independence Day party.The couple have three children, nine-year-old twins Hazel and Phinnaeus, and seven-year-old Henry.It was recently claimed Julia and her family are keen to leave Hollywood and move to Hawaii permanently so they can "live off the land" and surf all the time.A source previously said: "Julia has been into healthy eating for some time, but she got even more interested in it after deciding to lose the 10 pounds she, gained while playing the Evil Queen in 'Mirror, Mirror'. "She's even considering moving to Hawaii, where her family vacations every year, so they can live off the land, bask in the sun and surf 365 days a year."