Nope! It's only considered cheating if 1 person is accessing both accounts and is using them to give themselves money or other resources that should be earned fairly. If it's your sister's account, you ought to be fine, but transactions between your account and hers may be looked at with more scrutiny than normal just to ensure that nothing fishy is happening I'll make a note of this so that when your sister sends in a registration it won't be held up because of it being flagged for the same IP.
One thing I've found with the centre tags is you need to be very particular about the spaces before/after the tags and between lines. Otherwise they go really silly if you leave out the spaces. I've had posts almost as messed up as that one due to it, but fortunately I was able to fix them.
@Luke-Teth I have triple checked to make sure there are no additional spaces before or after the name. At this point, would it be better to just remove him from the pedigree? His registration is still pending due to this issue, and I reall would like to get him competing soon.