The relationship between a man's attachment to his family and his testosterone levels is complex. As men become more involved with their families, it can lead to a decrease in testosterone. This reduction in hormone levels is particularly noticeable during significant life events, such as the birth of a child. Expectant fathers often experience a notable drop in testosterone, reflecting their emotional and psychological adjustment to impending fatherhood.

Additionally, even brief interactions, such as holding a baby, can further lower testosterone levels. This suggests that increased family bonding and nurturing behaviors might signal a shift in hormonal balance, fostering a more caregiving presence in men. Helen Fisher's book, "Why We Love: The Nature and Chemistry of Romantic Love," explores these fascinating dynamics between love, hormones, and human behavior.