我地都唔知個男人有咩咁吸引我妹妹
=> It is because they are the same type of people!
Both of them don't like working.........
both of them want to use parents' $ ....
both of them want to live in parents' flat (don't need to pay rent).......
both of them want to 'eat' in parents' falt (don't need to pay living expenses).......
both of them want to be take care by parents (don't need to employ bun bun / yan yan when having kids)
.....................
So your 妹妹 loves him very much. They think the same, they plan the same, they do the same.