Just before the year’s end, add one more celebrity split to 2010’s lengthy roster. Rocker John Mellencamp and his wife Elaine Irwin are separating after 18 years of marriage, they announced on Thursday. The couple met in 1991 when Irwin, then a 23-year-old supermodel, was hired to pose for the cover of Mellencamp’s album Whenever We Wanted. They were engaged just 10 weeks later. The couple is “proud of their 20 years together and are very happy with their accomplishments both as parents and as a family,” Mellencamp's spokesperson Bob Merlis told The Hollywood Reporter.