Ask yourself some questions:
Has this person contributed to the process of me becoming the person I am today?
Do I speak to them in person or on the phone at least once every three months?
Would I want them to invite me to a special life event of theirs?
Would I trust them to watch my children or my pets?
Has this person helped get me through a tough time in my life?
Is this person related to me by blood or marriage? If yes, do they regularly attend family events, holidays/reunions?
Do they know my birthdate?
Do I enjoy carrying on a conversation with this person?
Will this person have a good time at my wedding?
Will I enjoy having this person at my wedding?
If you answered "YES" to most of these questions, then invite them. If you answered "NO" to most of them, it probably won't be much of a scandal if you leave them off the guest list.