Resenting other people's happiness...

What is it about people who can't stand seeing other people happy? I mean when I was an immature young man I was jealous of people who was better than me but as I got older and more matured I learned to look beyond my own biased illogical emotions and be happy for people who deserve to be. Maybe the people who aren't happy that I have a ncie life actually think I don't deserve it. But when I mean don't deserve it I mean people who are bad or who got their life through cheating people or whatever, not through legal means. So what if I inherited my wealth? It's my luck in life. Why do people grudge that? A lot of parents grudge that their kids have a better life than them when they were young. Isn't that what parents want? A better life for their kids? But when they do achieve that they tear the kids down by using it against them: 'oh you kspoilt brat, you know during my days we had to suffer so much, you don't even know. You haven't gone through anything worthwhile, you're all chickenshit!' or something to that effect...I just wish people can truly be happy for another person when the other person is doing better than them, I think that will be another really big step to having a peaceful world.