their bank balances, properties/home in their name etc can also be shown as strong ties…how old is your sister? does she have her own savings? if she is older than 22, she should put through separate application i believe (confirm this with other experienced members here)..you will have to be careful when putting through sister’s application, if she is unmarried(my guess) n doesn’t have a job& savings of her own, it will be considered only if application is strong (when shez travelling with parents n brother already in canada, her ties to home is very less)