Rufus considers the question as he drinks some of the water he pulled out, wondering if "curiosity" was a legitimate reason, and knowing if that was all, he could have said nothing to Cloud. And saying it was for his own amusement, although true, wasn't the entirety of it.

"I suppose," Rufus caps his bottle, and gives Cloud a smirk that seems somehow different from his other ones. "I suppose there's this this little side of me that's curious what the other offspring my father has produced are up to. How different they are from me."

How Cloud takes that is up to him.