Is it normal to feel jealous of an ex's new partner?
Yep.Totally normal
Yes, it’s normal to feel jealous when an ex starts seeing someone new. The feeling can show up even if you don’t want to get back together; what matters is how you handle it.
An ex moving on can stir up comparison, hurt, or a sense of being replaced. That doesn’t automatically mean you still want the relationship—it may just mean the breakup still has tender spots, or that seeing them with someone new makes the ending feel more real.
Lots of people feel this, though some shrug it off and others find it really stings. Try not to turn the new partner into a measuring stick for your own worth. If checking their social media keeps reopening the wound, muting or unfollowing for a while is fair game.