Joey Lawrence may have cheated, but his marriage to Samantha Cope was reportedly doomed from the start. Cope shockingly filed for divorce from the Blossom actor on August 13, citing “irreconcilable differences” as the reason for splitting just two years after tying the knot. While Lawrence, 48, had allegedly been having an affair with his Socked in for Christmas costar Melina Alves, 40, a source recently spilled to a news publication that “infidelity isn’t the cause” of his and Cope’s breakup. “Not by a long shot,” the insider insisted, claiming Lawrence and Cope, 37, who share a 19-month-old …