The battle between the No. 1 and No. 2 most popular sites on the internet has been tense at times. Like when Facebook tried to take on Gmail with its email service. Or when Google tried to take on Facebook with its own social network. Or when Google blocked users from importing their Gmail contacts to Facebook. Or when Facebook blocked users from importing their contacts to Google+. Meowww!
But siblings have been on opposite sides of worse power struggles. Like two sons of the famed playwright Berthold Brecht, who were in rival armies in World War II (the one on the German side died). Or when it was standard practice in the Ottoman Empire for a new sultan to imprison all his brothers, and then strangle them all as soon as he produced a male heir. Eeeeks!