Oswald and Edward; married in the time jump.
Stay with me. Oswald and Edward are seen working together in the time jump. If Gotham is going to suggest that they have been operating as criminals, doing illegal stuff together for years, wouldn't it make sense that the two of them would have exploited the heck out of Marital Privilege? The law that protects the confidential communications between spouses during their marriage from being used as a testimonial in a court case? Meaning that one can never be forced to rat out the other? What a dramatic reveal that would be.
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Imagine it. After lying low for months, Oswald Cobblepot resurfaces and puts a grand scheme in motion. The GCPD knows its Oswald, so they grab The Riddler to question him because he likely knows all about said plan.
Riddler is in the cold interrogation room, all pristine in his green suit, bowler hat and leather gloves. Completely relaxed and in his element. Jim slams some files on the table and goes through how they know Edward knows what Oswald is up to.
All the while Riddler has this shit eating grin as he loosens his gloves, one finger at a time, as he listens to what Jim is saying.
“While I would love to help you out, Jim…” Riddler begins as he places his arm upright on the table, so his hand is almost eve level with Jim. A bit unnecessary but it allows him to be as dramatic as possible as he removes his left glove with a flourish to reveal a gold ring on his ring finger. “I'm afraid you can’t legally force me to testify against my... Husband.”
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“I don’t suppose you know anything about The Riddlers most recent escape from Arkham...?” a tired Jim deadpans to Oswald in the middle of a high-end restaurant, where the Riddler is blatantly seated across from Oswald. Martini in hand, smugly leaning back in his chair, still in his striped Arkham robes just to rub it in.
“...I'm afraid I legally can’t say Jim” Oswald replies with mock sincerity.