I can't say that I have met a lot of people like this. It is all about identity, and encouraging that person to find theirs. You are not the same as your brother, neighbour or friend. Who would want to be exactly the same as someone else? Whilst you may admire someone else, you have to be yourself, and follow your own path in life. You have to accept your limitations as well. Not everyone is cut out to be wealthy, famous, good looking, or charismatic, or whatever it is you admire. It is important to be happy that they have those things, but things aren't always as rosy as they seem. There are many things that they envy about you. If they are a millionaire, they probably worked long hours, possibly away from home. Their marriage may have suffered, and they may envy your happy and stable home life. It's important not to compare because any kind of success is not without sacrifice. If a happy home life, is not something you would ever sacrifice, then it sounds like you would not be able to be a millionaire, even if given the chance. It's all about values, and what you wish you had, may not be what you thought it would be, if you got it. Try to be happy with yourself and your own lot in life. The grass is not always greener as they say. Learn to love yourself, because you probably have many special qualities that your friend or sibling does not.
Whenever I encounter people who tend to compare themselves with others, I recall this passage from Desiderata: "If you compare yourself with others,
you may become vain and bitter;
for always there will be greater and lesser persons than yourself.
Enjoy your achievements as well as your plans."
I think it's more exciting to live life at a pace you're comfortable with and on your own terms.
I don't know that I have met people who do that. If you are talking about "keeping up with the Jones's"- I think that is completely shallow and shows poor character.
As an artist I find it hard not to compare what another artist has achieved artistically in the same class/ lesson or competition as me- not in a way to rank one as better or worse. Often a teacher will positively critique each students work so we can learn from each other. It might not be the type of comparison you are asking about.
In other situations I like to keep in mind the saying "comparison is the thief of happiness ".
I have met a few of these people since having my children. Having your child's development compared to that of others only adds to the angst of parenting and the constant worry that I am not doing enough, so I try not to think about what others have said, tell myself that all children develop at different stages and most of all, don't even bother worrying about something that for the most part, I don't have a lot of control over. If push comes to shove, I avoid them!