If you have a long chat list in Gmail, then its clear that you must be having a lot of Contacts in your Gmail. A lot of contacts means chances of having Duplicates are possible. I have many friends who constantly keep changing there Gmail ID and sometimes when times comes to send them important mails, you are confused which was his actual account ID.

Find Duplicate Contacts in Gmail and Delete Them

Better way is to delete those duplicate contacts (Email ID which are not used) or else merge it with the same account holder name. This can make your Gmail looks clean and neat.

Those are duplicate contacts in my Gmail ID.