i was wondering if this lines are right
"mukashi mukashi aru tokoro ni 3tsu no yuujin ga imashita . aru hi , 3tsu no yuujin wa Seikatsu ga hanashimashita"

Question

i was wondering if this lines are right 
"mukashi mukashi aru tokoro ni 3tsu no yuujin ga imashita . aru hi , 3tsu no yuujin wa Seikatsu ga hanashimashita"

Answer

You can say "3nin no yuujin" because "3tsu" is used in "things", not in "people".

I did not understand this phrase "Seikatsu ga hanashimashita".
Do you mean "They discussed about thier everyday life"? If so, you can say "3nin no yuujin wa jibuntachi no seikatsu ni tsuite hanashiaimashita."