Valid reasons to guarantee return to china after visit

[pmoyse]

We are having difficulty getting my fiancees parents visas to canada from china.
they were denied visas because there was not enough reason to guaranteethey would return to china after the visit

Any tips or advice on how to show that someone will return to their home country?
we showed their deed to their apartment, retirement pension, and the fact they have two daughters and two grandchildren to return to

HELP!!!