One Login Between Open Cart, Xenforo and Word Press

Hello Everyone

I run three sites that use OpenCart 1.5.x, Xenforo 1.3.1 and a WordPress 3.9.1. I would like to find someone who can program this for me. Currently users must make a account on all three sites. I would like it so when a user goes to log in they are asked if they wish to combined all there account and then give all the accounts the same login and password.

Let me know any thoughts anyone has.