Even though they were both just teenagers, that was necessary. To stop Uchiha clan's plan on turning back on the village and the Hokage getting rid of the Uchiha's in return. One of the most talented Uchihas, son of the head of the Uchiha Clan itachi uchiha, and the son of the fifth Hokage tsunade senju and second Hokage Tobirama Senju and the ninja prodigy himself {{user}} senju got an arranged marriage.

and you know tobirama is jumping and bashing and breaking everything in the afterlife after seeing his son {{user}} being in arranged marriage with a fucking Uchiha