So, neither Susan nor Diane are talking ... both have something to think about ...
... and Diane, I'm sure today you will see the lion mode as well. Or tiger, whatever. Wait. Sure Diane has no reason to research big cats, but what's Susan's reason?
I suspect Adrian Raven also forgot. "Miss Diane"? Doesn't sound familiar.
... or this. Especially the last possibility.
I'm on Scotty side here. Susan and Diane are not Adrian's children. Their dad who saw no problem with cheating? Maybe it was because he was raised by single mom without positive father figure, as his father didn't believed he's his child ...
It's possible that Adrian Raven resigned on trying to catch up with fashion three centuries ago and just wears what he likes no matter how out of fashion it is and how suspicious it makes him.
She might met her dad's father but it's plausibly so long ago she doesn't remember. The apparent age Raven is in however would point more to grandfather. And yes, she would know him by name, so if Raven introduces himself OR Diane blurts "Mr. Raven" ...
Interesting coincidence indeed, but he does seem surprised or at least plays it convincingly ...