"Noooo! They can't be brothers, they have far too much chemistry!" - precisely, though if it turned out they were that'd make Ainley!Master's perving just as bad as Susan's.

Clearly Susan doesn't know anything - she doesn't even notice the man she's calling grandfather doesn't actually look anything like her grandfather ;)

It's Princess Margret I think, and her sheer polite indifference when Turlough's making obscene hand gestures and talking about how big it is is just the bestest.