This is excellent science fiction, and made me think briefly of Ted Chiang. Like my favourite science fiction, it has less to do with the future than with people. When I realized where things were going I gasped. This is the introduction:

In the summer of 2065, driven by a series of mass agricultural failures and growing overpopulation concerns, the Chinese government announces an exorbitant new tax on families with more than one child. For parents with terminally ill/bedridden children, a new brain–body exchange technology is offered that will allow them to temporarily lend their bodies to their children—an unprecedented chance at adulthood, but at a life-changing cost.