The term "twin brothers" refers to two siblings who were born at the same time, sharing the same mother's womb and often having similar physical characteristics. Twins can either be monozygotic (identical) or dizygotic (fraternal). Monozygotic twins occur when a single fertilized egg splits into two separate embryos while in the uterus, resulting in siblings with identical genetic makeup. Dizygotic twins result from two different eggs being fertilized by two sperm cells at the same time and developing separately until they join together to form a single placenta. In both cases, twin brothers are born within minutes or hours of each other and often share similar interests and experiences throughout their lives.