Good, better, Best. Bad, Worse, Worst

Hello all.

I have been thinking about this for quite some time, but I never knew
how to go about it.

I wanted to gather evidence for my thesis that in all IE languages,
the comparative and superlative of 'Good' and 'Bad' are always formed
from another stem. This works for the adverbs as well.

I know an example from Romance:
Port: bom (adj), bem(adv), melhor (adj, adv comp and sup),
mau (adj), mal (adv) -> pior (adj, adv comp and sup).

Engl: good(adj), well(adv), better (comp), best(sup)
bad(adv), badly(adv), worse (comp), worst(sup)

Can anyone prove or disprove this statement?