Create lists of equivalences from pairs

ConnectedComponents[Graph[ex1]] would be easier.

ConnectedComponents[ex1]  

{{6, 7, 8}, {1, 2, 3}, {4, 5}}

FixedPoint[Union @@@ Gather[#, IntersectingQ] &, ex1]

{{1, 2, 3}, {4, 5}, {6, 7, 8}}