Okay, that's too casual of a mention for someone who's just heard of him.

"How do you know me?" He manages to say before Yelena's next words register with him. His body stiffens at Natasha's name, the name of someone he owes amends to, but he couldn't give them proper since she was already dead once he started that particular goal.

Sister. He gives Yelena a proper look, now - her stance, a look in her eyes he recognizes in others that have been through so much - and he sighs out, "You're a Widow?" Or was, at least.