Breishit 36:21 list דישון as the son of Se'ir, but verse 25 lists him as the son of Ana, which would make him a grandson of Se'ir. Which is it? Why the contradiction?
According to Da'at Mikra, it's not a contradiction. On verse 36 they write that there were two Dishons and one Dishan. On verse 21 they write that Dishon was a common Horite/Hurrian name. There are many examples in Tanach of people whose children shared names with their parents' siblings (example 1 (Elpa'al being the father of Zevadiah I and Bri'ah), example 2). Moreover, note that Dishon ben Seir is spelled דישון while Dishon ben Ana is spelled דשן. And Dishan is spelled דישן.