Benjamin Sisko exists in the Mirror Universe. Given what is revealed in the first story arc of Season 7 about the regular Sisko's parentage, this is highly improbable.
Kira states to mirror-universe Kira that she has never heard of Kirk, as he is part of human history. Yet later she uses the phrase "through the looking glass", indicating that she is familiar with the human phrase from "Alice in Wonderland".
The alternate universe Quark addressed Kira as 'Major', but Kira never mentioned her rank to Quark nor is it shown how he learned this.