Immigration Forum / Canada / March 2008

Hi
Here's my situation:
 - Got PR stamped in passport in Mar-2008
 - Currently living in US on H-1B visa (citizen of India)
 - Planning to move to Canada in May-2008
 - Only other sibling also lives in US on the way to becoming
permanent resident of US
I want to apply for visitor/tourist visa for my parents in New Delhi
so they can join us in Canada for a month or so. Here's the summary
about their situation:
 - Dad is retired gov't employee and active businessman (farmer). Mom
is housewife
 - Traveled to a few countries during the last couple of years on
tourist visas (Singapore, Malaysia, Thailand etc)
 - US tourist visa was rejected twice in 2005.
 - UK tourist visa was rejected once in 2007.
In this situation, what are the chances that they can get a visitor
visa to Canada is they apply immediately after I move to Canada in
May-2008? What is the criteria for getting a Canadian tourist visa?
Does the applicant need to show "strong ties to the home country" to
prove that they will return after their brief visit to Canada? Thanks!