It should be remembered that the dis- in disheveled and disgruntled is not a negating prefix but an intensive. The OED definition of sheveled (and the definition given in tsuwm's wwftd list) matches that of disheveled. Gruntled is not listed on its own in the OED but it's related to the second meaning of the verb definition for gruntle, 'to grumble, murmur, complain.'