I have definitely been jealous, but it has always been towards other people's overall relationships, especially ones that are happy and "open." For example, if I don't get along with a brother or a sister, and I see another person having the best of relationships, I can see myself getting jealous easily.
This is the only thing I get jealous of. It's hard to see people in healthy, happy relationships and people who are able to be so open about their feelings for the other. This comes from me being an unemotional robot that sucks at relationships