Vincent can't see the way that Irahl's eyebrows raise in surprise, but the sounds of fridge-rummaging pause as he glances over. There are a couple of different points of interest to Vincent's revelation, and none of them are things that Irahl could have guessed if he'd tried.

A few questions come to mind then, and he wonders if they might ever be answered or if it will remaining a curious mystery--because there's no way that he'll be the one to ask any of them. Maybe Vincent will corner his brother about it at some point and Irahl will hear the results by proxy.

Along with this, there's another thing that Irahl finds himself surprised by, and he has no idea why he hadn't considered the possibility before now. Vincent says 'our unit,' and Irahl realizes for the first time that Vincent and Seth could have both been in the military together.

A couple of things make way more sense in light of that as a big chunk of context suddenly falls into place.

Irahl finally finishes his scavenging and lets the poor fridge door close, grabs a glass of water at the sink, and heads back to his seat on the bed.

"Well, they were alive and took me smashing up their obstacle course very well."