i am afraid if blizzard ever does find it out that they can ban your mage (and possible the rest) since you don't have the same names in the account creation
a friend of mine and her husband both played wow, they played eachother accounts a bit for fun, she made an alt on her husbands account, couple of months later wanted to bring it to hers ... and they banned them both. They mailed everything and such saying their husband and wive but they never replied (mind you this is EU .. heard the american GM's are allot nicer and helpfull)