Complex sentence: According to the legend, soy milk was developed by Liu An, who made it for his mother who was old and ill but wanted to taste soybean, which her teeth would not be able to chew.
Split into simpler sentences: According to the legend, soy milk was developed by Liu An, who made it for his mother. His mother was old and ill, but wanted to taste soybean, which her teeth would not be able to chew.