Complex sentence: Although Remus Lupin believes that Andromeda and Ted are displeased by their daughter's marrying a werewolf, it is never overtly stated by either of them and can perhaps be attributed to Lupin's understandably bleak outlook on how werewolves are treated by most of the wizarding world.
Split into simpler sentences: Although Remus Lupin believes that Andromeda and Ted are displeased by their daughter's marrying a werewolf, this is never overtly stated by either of them. Remus' view can perhaps be attributed to his understandably bleak outlook on how werewolves are treated by most of the wizarding world.