Aaron Carter's messy breakup just got messier. According to TMZ, the 31-year-old was granted a restraining order against ex-girlfriend Lina Valentina after accusing the woman of physically abusing him and threatening to stab him with a knife. The order was filed on Monday in LA County Superior Court against Valentina, who Carter claimed would shove him and hit him in the face throughout their relationship. Nick Carter's younger brother also accused his ex of threatening to stab him several times with the knife she allegedly carries with her. Aaron's ex had recently been named by . . .