According to Urie Bronfenbrenner, child’s development is affected by the multilayer system of different factors by analogy with the ecosystem. It has five levels: microsystem, mesosystem, exosystem, macrosystem, chronosystem.
To the microsystem belongs the closest factors, such as parents, school, home, peers, teachers. Those with whom a child contacts directly and constantly. Mesosystem is the links and connections between the different elements of the microsystem. For instance, parents and teachers relationships. Exosystem includes the external factor that the individual doesn't have an impact on. Like parents’ workplace. Some changes in the career of parents influence the child as well. Macrosystem cover the cultural context. Social norms, standards, values, laws and traditions.
Look at the picture
The closer the factors are to the individual, the more influential they are. However, what is important is that these systems are not independent one from the other. The ‘smaller’ circles are determined by the ‘bigger’ ones.
Now considering your questions about the children left by the parents and Bronfenbrenner’s theory. Parents belong to the microsystem - the closest and the most influential one for the development of the child. We can make here two conclusions:
1. To provide the balanced environment for the child in the parent's absence we need to develop the most favorable correlation of the factors belonging to the microsystem: school, neighborhood, classmates, close relatives etc. There is no equal substitution for parents, still, according to the Bronfenbrenner’s theory, they are not the only ones who form the microsystem.
In short: we need to strengthen the other elements of the microsystem, to give a firm base to a child’s development.
2. As the ‘smaller’ systems are determined by the ‘bigger’, the very fact that parents have to work abroad is the results of the exo- and macrosystems. So to solve the problem of guest working we need to find and fix the bugs of the bigger systems.