Yes there is. The 717 is almost entirely structurally the same as the DC-9-30 except for some added frames, which is different then the MD-80. The MD-90 is based on the MD-80 but the 717 is not.Those are all part of the DC-9 family. I don't know if there's any way to say they don't all build upon later generations.
Avionics is a different story. The 717 avionics is based on the MD-11.