For the first time, Ponyboy wonders about what Bob Sheldon was really like after glimpsing his picture in one of Sodapop's old yearbooks. Bob's dark eyes reminded Pony of Soda's and the Shepard boys' and Johnny's eyes. He wondered what Bob had been like--that he liked to pick fights, that he was a buddy to Randy. Did he have a kid brother? Or a big brother? Did Bob's parents hate Pony for causing his death? Pony decides he would prefer to be hated than pitied, but for the first time "I could begin to see the person we had killed."
Basically, when Pony sees Bob's picture in the yearbook, he just starts to wonder about Bob as a person. He had never really thought of what Bob was like -- he had just seen him as a sterotypical Soc who was always a jerk (or worse) to the Greaser types.
But now he starts to wonder about Bob. He wonders about the Bob that Cherry Valance knew. He wondered about whether Bob had a brother. He wondered how it was that Bob was (according to Randy) the best friend a person ever had.
He wonders a lot of things like that, but the overall idea is that now he is seeing Bob as a real person.
For more details, look this up in the book -- it's right at the start of Chapter 11.
For the first time ever, Ponyboy considers the idea that Bob is an actual person. Before this moment in chapter eleven, Ponyboy never gave a thought to the fact that behind the tough Soc exterior was an actual human.
I looked at Bob's picture and I could begin to see the person we had killed. A reckless, hot-tempered boy, cocky and scared stiff at the same time.
Ponyboy wonders whether Bob had a loving brother and parents.
Did he have a kid brother who idolized him? Maybe a big brother who kept bugging him not to be so wild?
During this section of the story, Ponyboy once again turns his thoughts to Cherry. Even without being there, Cherry is able to steer Ponyboy toward a clearer picture of the Soc and Greaser dynamic. Ponyboy knows Cherry, and he likes her as a person, despite the fact that she is a Soc. He knows that Cherry saw something good in Bob. Ponyboy realizes that if Cherry saw something good in Bob, then there probably was something redeeming about him in the first place.
But what about the Bob Sheldon that Cherry Valance knew? She was a smart girl; she didn't like him just because he was good-looking. Sweet and friendly, stands out from the crowd— that's what she had said.
This yearbook sequence in the story is a great continuation of Hinton's efforts to show readers that the Greasers and the Socs are more alike than they are different.