I want to edit the login script somehow to check the users ip and if then somehow look through the accounts and if the ip matches a different account then ban the one they are on. Does this make sense? If its to hard/impossible then don't worry but it would be nice to have a little help, i have no idea where to start

I think that's not a good idea.
Do you mean matches an ip that's online at this moment?
In this case you perhaps ban family members (brother, father, mother ...).

If you check the ip versus a saved ip, you perhaps ban a player of a provider, that uses dynamic ip's.

You better log the account on login if that matches another ip and do the check if it is a double account by testing the two accounts manually.

What Pierce said. If you do this, you WILL ban innocent accounts.

I have a program that connects to POL via AUX script and stores all the info POL sends it in a relational database. One of the things being stored is login info, so that it can be queried with SQL.

There are numerous accounts that, by looking at the login history, are clearly different people that live in different places - but which occasionally have gotten the same IP address due to their ISP.

I know this for an absolute, 100% fact: Because one of the matches is between my account and someone else's.

Plus, friends share accounts sometimes. Doesn't matter how stupid you tell them it is, they do it anyway.