I'll take a wild guess - they get jealous of charismatic types
All my jelalousy is firmly rooted in Leo. I don't think anything makes my Pisces twitch.
I don't get jealous. People are better looking, taller, smarter and funnier than me. I enjoy their traits. I don't get jealous of my husband. If I didn't trust him, I wouldn't be with him.
When someone you love deeply has a connection of a sort with someone that you will never have with them. It's a sort of loneliness/jealousy.
Also people who are very organized and on top of things in their lives make me jealous sometimes. They don't get into trouble and have to dig themselves out due to spacey-ness!
I <3 charismatic types. I can be too on a good day!
Agree with luci (#8) and starkttn (#10) first paragraph
Connection is important to me (read: partnership) -- Jealousy can raise its head IF the connection vibe is different with someone else.
Pisces are jealous of people who are more emotionally affective.