[Because they're worried about you, you big idiot!
He's quite surprised when Ianto seems so calm about the idea of Spike leaving, but he's learned to defer to Ianto on matters of Spike so he doesn't make a big thing about it, just snuggles against Ianto even more.]
Mmm, fine, if you don't want to snuggle we'll have to make do with just the two of us, then.
[Then he opens his eyes properly to give Spike a straight look.] We're here if you need us, though, right?