Relief...thats all I felt when I found out I was a man ( Gender a biological concept?)

Two days ago while frantically preparing for my exam, I came a across a story in my in psych book about a boy raised as a girl. The mother was pregnant with identical twin boys. Months after their birth, one of the twins sustained an injury that damaged its sex organs; a botched circumcision that caused massive bleeding and later infection. During their son's surgery to remove the infection, the parents decided that the surgeon should continue to remove his entire penile organs and create a vagina instead.