Don't worry, I know lots of people in a similar position - I didnt originally know Minnie's age but was lucky that Petlog had a record of her being chipped in 2000 as a kitten, but I still don't know the month she was born so she could be six or seven. Like Desley, I've given her the date I adopted her on as a birthday - June 5. The insurers will never know your cats' real ages anymore than you do! I guess if it was a problem they would start asking people whether their cat's age is known or guess-timated, but I'm not aware of any insurers who do.