I think literature--the really good stuff, not just any writing--is more like a mirror which reflects those social, political, and economic issues in any society at any given time. We know, for example, there were too many orphaned children struggling to survive in London in the mid-1800s. Dickens didn't create that truth, but he did reflect it in his novels. Literature is the mirror which reflects the truth of both human nature and the human condition (social, political, economic, religious) in all times and all places.
Just to cite one example that might serve as a way in which literature influences society, postcolonial literature from writers in Africa originally stems from a postcolonial society, of course. But when read by someone from another society, it influences what that someone knows, thinks, understands about the postcolonial world. Even though the literature was reactive to start with, it certainly could be influential later on.
And this is really the case in all scenarios. It's hard to believe that literature that reflects society, never gets read by someone who then acts on what they've read to form the future.
Most of the time, I think literature is a result of what is going on in politics, economics, or society as a whole. People become disenchanted, angry, depressed, whatever emotion you want to name, and they write about it. Take, for instance, Thomas Payne's Common Sense written just before the American Revolution. Les Miserables, Fences, A Raisin in the Sun, and Letters From a Birmingham Jail are just a few other examples of how people write to react to injustices going on in their lives. I wonder what will be published as a result of this healthcare system we're about to get?
I think it would be challenging to actually identify literature that does shape sociology, politics, or economics. I think we can find examples of literature that has had impact on political or world events. Yet, to make the case that literature is the origin of these experiences is quite challenging. I might offer up that literature is shaped by and reflects the domains of sociology or politics. I think this might be easier to analyze and demonstrate some level of proof.
I do not really think that most literature shapes the relations you mention. The reason that I do not think this is that I do not think that enough people are exposed to real literature or care enough about it to actually have it affect their lives and the way the relate to others.
Literature to be intelligible and meaningful to reader must have some connection with the reality as it exists. But this does not mean that the literature only reflects the society as it is. Literature may contain many other type of information like, evaluation of what is considered to be good or bad in the society, causes and possible remedies problems in society, a vision of a different kind of world. This different kind of world may be a vision of a better world or worse world extrapolated from the characteristics of the current world. In this way literature also contributes to bringing about major changes in the society.