aeque

Aeque is the adverb of aequus, "level, fair", and it does two jobs. On its own it means "equally" or "fairly", of a share or a treatment. Followed by ac or atque it becomes a comparison of equality: aeque fortis ac frater, "as brave as his brother". That ac is not optional decoration, it is the second half of the construction, and quam appears there only in later Latin.

Two things to watch. The double e is a diphthong, ae, and writing eque is a spelling mistake rather than a variant. And do not read it as a synonym of pariter: pariter stresses that things happen together, side by side, whereas aeque stresses that they are the same in degree. English equal, equity and adequate all come from the parent adjective.