I am going to be in a similar situation where my parents had me at 19-20, divorced, and for my first 18 years I lived in a 2 room apt with my mother. I now have a little brother who will be 2 years in January but these days pops and his new wife are living in Buckhead if that gives you any idea.

I won't say that I am necessarily jealous, but it definitely would have been nice to have the same advantages in life that I know he is going to have from the get-go (I'm 20k in student loan debt, worked full time through school, and currently doing shitty internships at 26 years old to get into a decent industry). My fiance however was born out of the country and has experienced poverty beyond my wildest dreams to the point that I essentially look like the rich kid, which is hard to swallow for me even after 3 years... So it's all just a matter of perspective (just as I'm sure there are people who would view HER as the rich kid depending on their upbringing).

Love your sister unconditionally, be humble, and concentrate on being the best man you can be in spite of the obstacles you've had to overcome. Or conversely let it eat you alive and become a d-bag... lol... your choice.