Ooomis,
The Amaranthaceae are a large family of plants, about 100 genera and a couple thousand species, in the super-family of the Magnoloids. The genus Amaranth includes dozens of species which exhibit wide variability in form and color. You may be familiar with several species referred to as pigweed.
Botanically, morphologically and genetically they are very distant from the grasses – which include all chametz. They are very slightly closer to the legumes. If we were talking about animals the distance between amaranth and chametz would be, say, dogs to sea urchins – both animals with circulatory systems. Amaranth to peanuts would be cockapoos to cockatoos – same number of limbs, both have a backbone.
The species which are normally eaten are native to Central and South America but are now cultivated all over the world. The leaves are normally eaten although the seeds have become popular again due to their high protein content – particularly rich in lysine – and ease of digestion for celiac disease sufferers.