Xero as a finance system doesn't need to worry about the person/organisation in the same way that Sheep does. Sheep will try to do the right thing in understanding which entity (the person or the organisation) should get the Xero connection. However there will always be cases where the wrong decision is made.
How to move the Xero connection from a person to an organisation (or between any 2 contacts).
Copy and delete the wrongly attached identifier
Navigate to the 'Meta' tab on the contact
Find the Xero identifier
Copy the identifier
Delete the identifier
Create a new identifier
Navigate to the target contact and again go to the 'Meta' tab
Click 'New External ID'
Enter 'Xero' as the system/service
Paste the identifier you carefully copied earlier
Finding the Xero ID
If you want to create the connection yourself you can find the ID for a contact by loading that contact in Xero and selecting the ID from the URL.
The ID is a sequence of numbers and letters between the slashes (/). These IDs are used for all types of data in Xero - make sure that you are viewing the contact not, for example, an invoice for that contact.