This was my approach to things even as a kid. I didn't care who got the bigger "half" between my brother and I, because I wasn't going to care once I'd eaten it. All I would remember is that I'd eaten it :)
It's usually not so much jealosy as a sense of fairness. Sometimes that judgment is skewed, maybe they don't remember they had the largest part last time for instance, but kids tend to be ok with situations they percieve as fair and very unhappy with situations that seem unfair.