Should childcare always be free just because a parent is related to the person providing it?
Finding a good babysitter is the ultimate challenge for any parent who still wants to have some form of a social life that doesn't always involve their kids. There is nothing wrong with wanting some time that is adults-only now and then, but this is something that is likely to come at a price. The person who is most likely to take on any childcare duties without complaint is the one who is getting a paycheck out of it.
Of course, most parents would argue that it isn't unreasonable to expect a family member to provide some free babysitting now and again. Most moms and dads hope that they have some kind of village to fall back on when they really need it.
However, there is a big difference between generous relatives offering their help on their own terms and expecting them to watch the kids at the drop of a hat. Even the most willing of babysitters is likely to get a little bitter if their childcare becomes something that doesn't even warrant a proper discussion. Although the topic of compensation can be controversial when a family member helps out with the kids, it is sometimes appropriate to bring it up. For younger babysitters in particular, this may be one of their few forms of income, and it makes it worth it to give up their free time in favor of caring duties.