Aside from the external stimulus and challenges we encounter in life, the major factor that contributes to the development of our personal behavior is our childhood life. The personal relationship we have with our parents starting from the infancy stage enables us to develop our acquired temperamental traits. Eventually, the personal traits our parents have molded during the first five years of our life will be subject to change as we learn to interact socially with other people.It is a common observation that despite the fact that parents have provided the same parental care techniques under the same environment to each of their children, there will always be a very high tendency that our brothers and sisters will behave differently from us. The differences in our personal behavior as compared to our brothers and sisters often lead to conflicts and petty misunderstandings.Analyzing the behavior of another person using the widely used developmental stages theories by Eric Ericson (1956), Sigmund Freud, Abraham Maslow (1954), and Jean Piaget (1972) enables us to determine and understand the impact of another individual’s past life experiences on his or her visible personal characteristics at the present time. Being able to understand another person’s past life experiences allow us to develop an effective way to deal with their negative characteristics and traits.Based on the summary, the researcher will apply the theories mentioned in order to allow the researcher to develop a better understanding of their current attitude and behavior as well as their achievements in life.The purpose of the research study is to develop a thorough understanding of the factors that contribute to the development of my three brothers’ current attitude, behavior, as well as their individual achievements in life.The research study is intended to empower the readers to develop awareness concerning the importance of knowing the significance of the developmental stages theories in dealing with our siblings as well as the people around us.