Nathan sometimes sent him articles about science and asked questions about engineering projects Brian’s firm had supported.

Zachary exchanged shorter emails, mostly about practical matters.

Neither boy suddenly called him Dad in the familiar way they had once hoped to.

Both were slowly learning who he was.

One weekend Nathan told me he and Julian were planning to attend a robotics event together.

Brian would drive them if his schedule allowed.

If it didn’t, Julian’s mother had offered to take them.

Nathan said the plan was written down with a backup arrangement.