Cross Referencing Between Posts How Do I?

Hello, attempting to cross reference between posts effectively and failing miserably.

What do I mean by cross referencing?
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Posts

Category A: People
——————
1. Joe Bloggs
2. Jane Doe

Category B: Places

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1. New York City, NY
2. San Francisco, CA
3. Portland, OR

I want to cross reference between my two categories, example:

Person 1. Joe Bloggs to show that he’s lived in Places 1. New York City, NY & 2. San Francisco, CA

Person 2. Jane Doe to show that she’s lived in Places 1. New York City, NY & 2. San Francisco, CA & 3. Portland, OR.

Targeted End Result
——————–

So When I visit the posts for
– Places 1. New York – shows related people 1. Joe Bloggs & Person 2. Jane Doe
– 2. San Francisco – shows related people 1. Joe Bloggs & Person 2. Jane Doe
– 3. Portland, OR. – shows related Person 2. Jane Doe

How Can I achieve this so that the posts are always in sync, without having to manually update each post?

Comments and Ideas welcome.

Thanks in advance