Im having to teach my family development class this coming thursday on sibling rivalry. Im in need of two example situation for the class to solve about sibling rivalry. can you help

Yeah I've two kids 11 and 7 who fight like cat and dog 90 percent of the time. i try to distract them but what works for one doesn't work for another because of the age difference, my son who's 11 is a bit behind developmentally and my daughter 7 is very intelligent indeed told to us by all her teachers from reception upwards. The problemn being my son was all keen to have a baby brother or sister, involved as much as he wanted from conception onwards, kind helpful and considerate towards her from day one turned on her when she was about 3 and a half years old. he likes to torment her and has said it makes him happy as he is bored so takes pleasure in winding her up. he is given alot of attention especially at her bedtime, she goes up at 7 and he gets 2 hours self time where he doesn't have share me at all.
hubby has self diagnosed 'crap with kids syndrome' may as well be single parent but hey ho! hope this answers all.