LOS ANGELES (Reuters) – A judge on Wednesday finalized an arrangement for Michael Jackson's nephew to serve as co-guardian of the late pop star's three children along with the kids' grandmother, who until recently had been solely responsible for their care. The decision by Los Angeles Superior Court Judge Mitchell Beckloff follows recent turmoil inside the famous family over the pop star's estate after grandmother Katherine Jackson was reported missing. She later turned up in Arizona with her eldest daughter and other family members. But due to her absence from her Los Angeles home, T.J. …