Well I am SURE they didn't.... they just know each other names bacause they read them on their foreheads... Of course they do, but where did they met before we currently do not know.
Why wouldn't they? They were the youngest sons of the most powerful clans back then. I feel like the "Yo" is a mistranslation but maybe it's just me. I feel like they don't like each other much >_>
That pic made me laugh so much i had to read it over again today, THE SENJU AND UCHIHA CLAN ARE REALLY A FAMILY THEY DO THINK ALIKE. Lol, As for the knowing part, YES THEY DO KNOW EACH OTHER. Look at the dads, seems like they bump fist several times.