17-year-old works on aunt's yard with 15-year-old brother, refuses to give him half of $30 payment because he didn't help in the front yard: 'It's unreasonable'

A fair day's pay requires a fair day's work.

This is a statement that, in principle, a lot of people are likely to agree with. In reality, though, what constitutes hard work varies wildly depending on the individual and the context. 

Almost all of us have slacked off on the job at some point, and so long as that doesn't happen every single day, it is not so likely to cause a major issue. However, things get more complicated when another person's pay is on the line. If they felt like they pulled more weight than you, they are not likely to be happy to share out their earnings with you.

Doing any kind of paid work with family can get complicated for a number of reasons, but one of these is that relatives have a higher chance of making extra demands of you. Family supposedly helps family, even if it does not appear to be deserved. In these situations, it can also feel more difficult to say no, as many believe that they have some kind of obligation to their family members. That, or they are afraid of bigger consequences if they do not give in to whatever they are requesting.