Icloud jumble

Mine and my wife's Icloud contacts, notes, etc. somehow were merged on her laptop. Now there are phone numbers, names,and pictures under contacts that do not belong under that contact. A plumbing part number I had in my notes was under a contact with a number I do not know. There are phone numbers and pictures of people we do not know assigned to our contacts. There are birthdays under contacts we do not know. How does this happen? What should I do?