You can apply for a visit visa for your father right away if you want to but there is no guarantee he will get one.
You can apply to sponsor him once you have shown that you make enough money to support yourself, spouse, dependent children of your own as well as your father.
You can not sponsor your brothers children under the federal system because they are not orphans since their mother is still alive. If you are living in certain provinces where there is a family stream, you may be able to sponsor them later when they are grown up if all requirements are met.
thanks a lot Leon, you have cleared many doubts. Will it make it easier to get Visitor Visa for my father if he shows enough funds for his expenses and actually carry the same to Canada while visiting me. Will that help? he has around CAD 10000 equivalent money in his accounts in India.