Catherine Zeta-Jones and Michael Douglas share more than just love! The couple celebrated their joint birthdays in a pair of romantic Instagram tributes on Sept. 25. Michael posted a throwback photo of him and Catherine at the very beginning of their relationship, revealing the moment he knew she was the one on the night they met. For her part, Catherine shared a cute selfie of her and Michael and she had fun in her caption too – honoring not only her husband's big day but also her own!