Jim,
All grasses are in the same family. The differences are the genus' and species. I'm sorry I didn't read your first question the way you were asking it. If you look at that link you sent me, you will see many Agrostis and Poas listed, as well as festucas (fescues) etc..
If you look bermuda (Cynodon dactylon) and bent are obviously both in the same family, but are very different turf grasses.
You are right that they are in the same family, but the genus and species is what dictates the differences in how grasses grow and look.
DPL11