Check if part of a column contains multiple values

Hi All, I'm looking to isolate cases where 2 values from column B are present within their own grouping as determined by column A. That sounds wordy but I believe this will clarify:

A B
1 Adam
1 Ben
1 Chris
1 Dave
1 Evan
2 Frank
2 Gary
2 Henry
2 Irene
2 Jon

What I would like to know is within the 1's if Adam and Chris are together (they are, and they shouldn't be) and either highlight their names or put an "x" next to them or something along those lines. Then I want to check if within the 2's if Adam and Henry are together (they are not, and they shouldn't be)... and so on.

Any help would be greatly appreciated.

Thank you!

What do you mean "Adam and Chris are together"? Do you mean if they are next to each other in the cells? Also, how should I know if I am looking for "Adam and Chris" and not "Ben and Dave" Is this information stored somewhere?

By "Adam and Chris are together" I mean that they are in group 1, i.e. they share a common value in column A. The relative location in column B is not important.
"Adam and Chris" vs. "Ben and Dave" vs. any other combination of 2 would be done on an ad hoc basis, this could be typed into the formula as needed or referenced in another cell. I've attached a sample which should help (probably should have done this in the first place...)

Group_check.xlsx

Thank you!

This is PERFECT, thank you!