parents have more time n young/ strong enough to take care of them, where 弟弟妹妹 have less time to be with them. that's y the parents usually love them more , may be they feel that they didn't have lots of time to take care of them
for me~^^
i think it's fair to have gain n pay
no pay no gain
i'm the elder sister @ home, i think it's gd to be a sister as i got more attention from my parents; n my little sisters are lucky to have a very gd family life as mum spoil them so much