Catherine Zeta-Jones and Michael Douglas had a double celebration on Saturday when they both rang in their birthdays.The longtime couple delighted fans when they both wished each other a happy birthday and shared photos and tributes on Instagram.MORE: Catherine Zeta-Jones and Michael Douglas' £3.6m house is another worldMichael was the first to post on Instagram with a throwback picture from the first time they met.WATCH: Catherine Zeta-Jones exercises in a bikini The youthful looking couple