The easiest solution...
go into Gmail, create contacts with the same name (just put the name in and save it), give it a few minutes to sync. The names will match up and wala their sync'd.
or create another contact, this time choose your Google account, not the phone account and create the name, and same result, the contacts merge. Same thing happens with sync'd Facebook contacts if you want to link them to a phone contact or Google contact.
you can also force a merge if the two contacts are the same person but don't have the same name. But I've found if they have an e-mail address in common and similar names, Android is smart enough to link them together.