We are not alone. We do not get to call God, “My” Father as if we had an exclusive relationship. He has saved many sons and daughters. Those who have come to him in faith, belong to him in community. There are no lone-ranger Christians. We are compelled even when we pray to recognize that we belong to God…together.
The “our” here is a large collection of folks. In the context of this prayer it encompasses people from every tongue, tribe and nation (Rev. 5:9, 7:9). It includes men and women (Gal. 3:28). It includes those who have been outcast (Lk 16:19-31). Those who were sexually immoral, those who worshiped idols, those who have committed adultery, those who were homosexuals, those who were thieves, those who were alcoholics, and former con-artists… anyone who has died to self and picked up to follow Christ (1 Cor. 6:9-11).
This is precisely the point where Christianity and radical Hinduism are extremely different. We say there is no karma, just sin. Repent and be saved. They say there is karma and what you’ve done in a previous life has set you up for whatever suffering you get in this life. So the high cast and the low cast people are not equal. Within Christianity everyone is equal. We were all sinners. We all come by the blood of the lamb.
Realizing this we acknowledge that we do not act in isolation. Our actions have consequences that affect the greater body of Christ. We will give an account to our Father about how we have treated our spiritual siblings and others. Earlier in this larger section of scripture known as the Sermon on the Mount, Jesus says:

“So if you are offering your gift at the altar and there remember that your brother has something against you, leave your gift there before the altar and go. First be reconciled to your brother, and then come and offer your gift” (Mat. 5:23-24).

When we pray, we are to recognize that we are not in isolation, our actions for and against our spiritual siblings count. Some of you have hindered prayers because you have grievously sinned against your brothers. It doesn’t matter how great your speech is, or how eloquently you can present your requests to God. When your fellowship is broken with your brother/sister in Christ then you will have difficulty in real prayer… I’m sure you could still get out a bunch of words, but authentic prayer comes from the heart. The Apostle Peter writing in first Peter pleads with husbands to honor their wives so that their prayers won’t be hindered (1 Pet. 3:7). There is no us vs them in the family of God…just us.