I don't think there's any rule that says you have to bring up your son's children when you're old. This is a common phenomenon, but it doesn't reach the level of a "must". Nowadays, many elderly people are willing to bring up their sons' children more voluntarily, and they are not forced to bring up their sons' and daughters' children, so there is a problem with this issue itself.
Nowadays, after the retirement of the elderly, basically there is nothing to do, every day in the neighborhood to play, and the elderly to help their sons and daughters with their children, in fact, also want to find something to do for themselves, plus be able to give their sons and daughters to share some of the pressure, in fact, but also to make them a little bit of happiness, because the old most afraid of others to say that they are not useful, of course, think of the When you're old, you want to do something worthwhile, not just eat, sleep and play every day, with nothing to aim for. Therefore, the importance of the elderly activities now is also particularly important, can not let the elderly idle after a completely in the mix of life, should let them also find the meaning of life.
On the other hand, elderly people actually like children, not to mention their own grandchildren, pro-grandchildren, I think they are often willing to take care of their own grandchildren, grandchildren, after all, is their own descendants, or the third generation, that kind of grandparents and grandchildren full of fulfillment at our age may not understand, so the elderly are not without their children, so the elderly are not without their children. The old man with the child is not without merit, now many children and their grandparents pro, and their parents to communicate with the contrary become less.
Lastly, I would like to say that elderly people don't have the obligation to bring up children, they help to bring up children because they want to help their sons and daughters to share the pressure, so that they can concentrate on their work, so that we should also understand more about them, and to bring up children's contradictions should also be more understanding.