[G'raha's smile slips a little, and his brow furrows in confusion. Maybe it's just a choice of phrasing, but 'grew up with' implies a certain amount of childhood, especially when you combine it with the 'young little thing' comment, but unless he's judging her age very badly, she can't have been that young when Val became part of her family, even if she left Corvos right after he did.

On it's own, perhaps he could dismiss it, but when you combine it with the vagueness of her responses and the way she outright ignored the question about Val's age... he doesn't want to be suspicious, but there's just something about it all that's nagging at him... he's protective of Val, he doesn't want to see her hurt.

He gives Val a slightly cheeky smile]

I'm sorry, my friend, I don't mean to embarrass you, but the very image of you running around causing chaos, even as a toddler, it warms my heart.

[He feels bad for lying, even if he tells himself that the mental image does warm his heart, whether it be his own memory or somebody else's, but he knows that's just splitting hairs. It's a test, though, to see how Maeve reacts - whether she corrects him or not]