I feel really quite annoyed with your sister,how can she say that,my friend has a rescue Staffy named Dylan,he was 9 months when she got him,he is amazing with her kids whose ages range from 15 down to 5,he sleeps on her 8 year old daughter's bed,and sulks most of the day whilst the kids are in school,he has had quite a lot of training,but I honestly don't think this has had anything to do with his affection for this rather busy family,I hope your sister can start to understand the breed instead of believing that all Staffies are unpredictable and nasty