CanadianJeepGuy said:His son is still a willing sponsor correct? Why could he not still be valid on the sponsorship of his son?
The only reason to list the wife as a co-sponsor was because the son didn't meet LICO to sponsor his parents on his own and needed to combine his income with his wife's to meet the minimum. This means that if the wife withdraws the application, the application no longer meets LICO and therefore the visa is no longer valid because the base criteria for qualifying to sponsor are no longer met.