Fevered speculation gripped the US after repeated claims that a "well-known Hollywood actor" donated the sperm for Blanket. The Home Alone film star is said to have donated sperm to help Jacko create his seven-year-old offspring - real name Prince Michael II - with an unknown surrogate mum. The two celebrities became firm friends after Culkin, now 29, shot to fame as a child in the 1990 box office smash.