Using some kind of client (such as Thunderbird) will allow both of you to check both accounts. Otherwise, you could set up a forwarding rule to forward everything from account a to account b (and possibly vice versa).
Just remember that if you forward emails through cPanel, it sends a copy to Gmail (or wherever), but leaves the original on the server. You have to remember to either download or delete mail from the server to prevent your inbox from filling up. (Or have a long-suffering spouse to do it for you. )