The lesson learnt is she did all that expecting something in return. You can’t fall in love with someone and just assume they are going to love you back that’s ridiculous. She was arrogant, he thought of her as nothing more than a sister. She wrongly assumed she would be better suited to be his wife all on her own.
Clearly he never even considered her a romantic partner as his clearly sexually experienced and presumably had relations with other women and she was never in the running even before the guy came along.
Don’t set yourself up for failure based on assumptions especially when to comes to love. The brother was an idiot. But at least they seemed to have learnt their lesson.
YESSSSSS THIS ANSWER MWAH MWAH
Imagine being amara and since child you've trained yourself to be fitted for a kings wife. Girly out there literally loving seren from the start and having nothing but pure feelings for seren, then suddenly she ask to his brother why can't it be her who deserves all the love. Then boogshh her brother wasted his potential and go off kill the uke just because his sister is down ( well I would to idk just I guess... ) Then wahhhh his brother got banished, BOTH of them. Man idk, ik that what seren did to both of them was understandable but. I think it's unfair for amara to be experiencing this when all she ever wanted was for seren to love her. But bogshh omg I guess that uke still got his happy ending so yeppers ( pls don't attack I just feel bad for amara cos yk she pretty and all like WHAT A WASTE OF BEAUTY )