Sorghum is in the grass family and is closely related to corn. In fact, when it's young it is nearly impossible to differentiate it from corn. If anyone ever tells you they have volunteer corn in their garden, you can sound smart by guessing that it's sorghum.
I planted broom corn a few years ago, and was amused by neighbours who pounced on it as proof that I was not gardening right!
One neighbour in particular would come by and remark: "You are doing something wrong! That corn is NOT forming cobs! "