How does one figure out the ''en'' of anden here? Is it idiomatic of hinanden? I know that the word was suggested but since we are referring to "we" I might have guessed "hinandre" or something...
"Hinanden" is always "hinanden", it doesn't conjugate like "anden"
There is the word hverandre, though, which is synonymous to hinanden.
Do note that hverandre is a bit archaic.