SharePoint lookup column won't display all related items from another list

Use case - I've created a list of competitors for a particular market. I've created a list of VIPs for that market. I've created lookup columns that allow me to associate a VIP with a competitor and visa versa.

What's happening - When I add a VIP to the list and associate it with a competitor, that VIP has to be manually added to the competitor item in the other list.

What I expected to happen - I expected that when I add a VIP and associate them with an item in the list of competitors, they will show up in the "Associated VIP" lookup column automatically.

My goal is to replicate low-level CRM behavior. In a CRM when you create multiple contacts and associate them with an Organization, that list of contacts automatically shows up on the Org record, I don't have to add them in a second step. 

How do I replicate this behavior between two SharePoint lists?