Complex sentence: With the keychain as proof of the misdeed, the kids come inside the apartment and confront Patty and Selma for their actions, threatening to tell Marge the truth about their involvement in Homer's kidnapping unless the twins pay for their parents' remarriage ceremony.
Split into simpler sentences: With the keychain as proof of their misdeed, the kids comes inside the apartment and confront Patty and Selma for their actions. Bart and Lisa also blackmail their aunts by threatening to tell their mother the truth about their involvement in Homer's kidnapping unless the twins pay for their parents' remarriage ceremony.