Apologies if this is skirting too close to the wrath of Vyndree, but I believe people in the past have done paid character transfers to get toons off accounts with a different name, ie Joe Smith has 2 accounts in his name and has toons on his brother Jeff Smith's account, he paid transfers them off to a new account in Joe Smith's name. Then he has 3 accounts with the same info. To my knowledge that's about the only way to "rehab" a situation of a shared account to make one pretty safe from scrutiny once multiboxing. In virtually all cases the answer I've read (as a noob to the hobby) is "don't risk it, it's an open and shut case for Blizzard to detect, prove, and ban for it. Besides with RAF it's cake to reproduce toons on new accounts"

Sounds like your last names don't match, which makes the above most likely impossible. So multiboxing with that toon invites the banstick.