In Jira, linking items together is easy and useful.

For example, you can clone an issue easily: Create issue 100, clone it to 101. 100 then shows "this issue has a clone: 101" and 101 then shows "this issue is a clone: 100"

Similarly, you can mark issue 201 as being duplicate of 200 (reverse is 200 is duplicated by 201), and there are a few other link types.

My question is around the use of related tickets. One side of the relationship is marked "This issue is related to ..." and the other side says "This issue is a relative of ...".

How does your dev team define those two items? It wouldn't matter much except the display is different, making the link types slightly different and it just looks like they are different when one issue is "a relative of" a few other issues, but also is "related to" some others....