Graph theory has widely been applied to probe physical properties in various solution systems such as miscibility, liquid-liquid phase separation behavior. Here, each component molecule is denoted by a dot, and the interaction between molecules is described by edge. Recently, we propose a hypothesis on molecular aggregation in aqueous solution systems. That is, some molecules tend to form self-associate aggregates while avoiding interaction with water, while others form spatially extended network to interact with water. In use of combination study of graph theory and molecular dynamics (MD) simulation, we revealed that this bifurcating aggregation pattern affects water H-bond structure and eventually solubility in salt solutions, miscibility in binary fluid systems , and phase behavior in binary liquid systems . Graph theoretical analyses in various fluid systems such as degree distribution, eigenvalue spectrum are presented to examine network properties of fluids and their effect on fluid properties.