And I don't mean in any pedophilic way, but when I watch this I noticed that he was more engaged with Benicio than Irene.

Benicio seems to immediately take to him, and trust him, and I think that meant a lot to the outcast 'driver', who longs to feel human (a real human being). Most look at him and say 'oh he's in his own world' but Benicio challenges him.

I see Benicio as the only person who's motives are pure and not doubted.

He carries Benicio ahead of Irene.

When he meets Benicio's father him and Benicio are in their own world that Standard has to repeat himself to get his attention.

When Standard is beaten he goes to Benicio first to see if he is okay. He decides to help the father for Benicios sake.

I think any doubt that he is more concerned about Benicio than Irene is at the diner when he asks how Benicio is. She says fine to which he replies "is he?", showing his distrust of her, and the fact that it wasn't just chit chat.

He says at the end that spending time with Irene and Benicio were some of his happiest days.

I think the Driver was always used to some extent, by his boss, by criminals, etc. Benicio only wanted to be his friend, and that made him feel human.