Unrequited love is a fairly common story. What’s unusual is that it seems to dog men and women fairly equally. There not many things that fit this bill.
As far as a marker in a chart goes, pining is a Neptune phenomena. Neptune tied up with Venus in any form, would be the thing to look for both in the chart of the person pining or being pined for.
These situations can be incredibly intoxicating. The pining can last for years. It’s not uncommon to see something like this last for a decade or more. The person pining often keeps their fantasy a secret.
I have Venus square Neptune in my chart. I can easily understand how these situations constellate as well as how and why they are sustained .
What are you experiences with unrequited love?