I have people in my contacts who I don't even know somehow, this has been like this for years.

So on Snapchat it says I have 480 contacts, It shows that I only have 60 on my phone as of right now. I think it might be a family member somehow and I'm 21 so I don't need that at all. How do I check to see who has access to my account and my passwords through keychain. I checked devices and it says there are only the ones I have.