list containing multiple items need help

Question

hi all im new to c# and ned a bit of help i want a list containing pairs of string not uniqe for example
mylist.add("bob", "steve");
mylist.add("bob", "ben");
mylist.add("ben", "steve");
 
and would contain
mylist[0] bob steve
mylist[1] bob ben
mylist[2] ben steve
 
how would i do this in code thanks.