Edward (sympathy) and Jasper (empathy) should not have been superficial or foolish. Luckily due to little writing Jasper escaped the brunt of the douchebaggery, but Edward spent four whole books oblivious to the consequences of telepathy.
These "brothers" could respectively sense what anyone was thinking or feeling.
Thoughts, as we all know, are not the same as speech. On rare occasion do we find it better to articulate while sentences to ourselves. Usually our thoughts are sloppy and sporadic, as anyone who has tried mindfulness meditation soon finds out. There are bursts of memory, emotion, song, and singular images attached to meaning without context.
Have you ever remembered a song but you cannot recall the words, tune, our even perhaps the meaning? Then what is left? What is that piece we hold onto? Those are the sorts of thoughts I imagine a telepath would find.
And then empathy, not just seeing another's point but viscerally feeling it as well. No wonder Jasper couldn't continue to murder sentient beings.
Most of conflict arises from fractured communication and, while it would be entirely one-sided, these brothers participated in pure and immediate communion with any sentient being.
There was no longer "the other" our even the unknown. All motives, however illogical or cruel, are completely contextualized.
I recall a throw-away conversation in hich Edward is talking about music (his character dearly loves music and I appreciate that) but then Edward dismisses all the music between 1960 and 1990. All the "devil music" I'm sure, but honestly I think a character like him should be able to find a way to appreciate quite literally every single song made. He has the ability to guess or actively know how that song feels in the artist's head. Imagine Mozart to Mozart's ears, imagine the grandness which he felt that he fell short of. Amazing.They should have been the most patient, sensitive and careful creatures imaginable. The one who talks you through your tantrum to the other side. The one who always "gets" you.
That alone would make them seductive and dangerous, as well as easily usurp their own characters, their own selves. As someone who is a mirror to others it would be a shock and a novel thrill to encounter a person you cannot reflect, a Bella who asks you to be yourself.