How do these come about, also what are the leading theories behind the formation of these objects?
I am not sure about this, but I think that dwarf galaxies are considered to be the origin or the seeds of bigger ones like the Milky Way. Currently existing dwarf galaxies are the ones that have not underwent enough collisions with others and have not accreted to form bigger galaxies. The current model of structure formation assumes a very violent history of mergers of structures that were accreting hierarchically. This process starts after recombination (the formation of the cosmic radiation background) at ~ 400,000 years after the big-bang. If I am right then you question is about the origin of galaxies at all.
Separate names with a comma.