To bring in your wife on a DP you must be earning at least $6K/mo in order to apply for a DP for her. You cannot sponsor a DP for your parents though. If you are making at least $12K/mo THEN you can apply for a DP for your parents, but in no case can you apply for DP for you in-laws (wife's parents). It is what it is. If you make less than $6K/mo it will not be difficult, but impossible. However, there is a slim possibility if she is currently on a DP under your existing EP, the with renewal they may continue to allow it for the duration of the renewal with the advice that you will not be allowed to renew it the next time without meeting the minimum requirements."
However, if your pass is canceled and you have to gain another pass with a new employer but still under the $6K minimum you will NOT be allowed to get a new DP for your spouse.