Sexy Hollywood star Sienna Miller is set to marry boyfriend Rhys Ifans after his third proposal, according to published reports.The actress is said to be planning a summer wedding with the 39-year-old actor, who first asked for Miller’s hand in marriage last August by sending her a cryptic message in Welsh, his first language, which read: "Marry the Misfit." He proposed for a second time in December at her 26th birthday bash by hiding an engagement ring in a pile of gifts.But the third time was lucky for the Notting Hill star after Miller accepted his proposal earlier this month. And the one-year couple is reportedly keen to keep their forthcoming nuptials low-key.A source tells British newspaper the Sunday Mirror, "Rhys has admitted he and Sienna are getting married. Everything is supposed to be hush-hush, but Rhys is over the moon and finding it hard to keep quiet. He can’t believe she finally said yes."Although Si and Rhys have a lot of famous friends, they will keep it low-key. They won’t be signing up to some magazine deal." Miller, who has previously called Ifans her soul mate, recently said, "I am in love - Rhys and I are the best of mates and life is going great."