My father and mother sitting next to each other. Figure 1 is a group of parents, but the parents switch 2 way ball well organized 4 people with parents, 1 round table seating group has all four ways! 2 (4!) = 48 method.
Father and mother sitting next to each other I think parents are combined into one group, but the parents themselves have two ways to switch the ball from one group held four people with his parents sitting at a round table four! All have two ways (four!) = 48 ways.
Mom and dad sitting together, think parents together as 1 group. But the parents own 2 switch method. A 4 people with my parents 1 group sit round table has 4! Way all the 2 (4!) = 48 ways.