Sirius knew that even if he could remember being alive during these years, he wouldn't have known her well. Before Dora joined the order, he had been locked away in Azkaban. He wondered if Dora's parents had told her the truth of where he'd gone, and the things they might have said when they learned of his apparent crimes. So many people believing he had killed James and Lily, but even now that they believed him innocent he still felt the weight of their deaths.
He smiled as she spoke of school, and of not becoming prefect, of being sorted into Hufflepuff. Though his pleasure of this knowledge was ruined by the recollection that above all things, Andromeda and Ted did not what their daughter becoming like him.
"I'm sorry that I missed it," he said genuinely.
Absently he took a bite of his sandwich, wondering at all these things he couldn't remember.
Sirius realised he could ask her about these missing memories, and expect answers that wouldn't be softened as Remus' were. He knew that his friend meant well, but that his desire to comfort often lessened the truth.