If we got the cast of A Thousand Splendid Suns to put on a stage production of The Wizard of Oz, then there's no doubt that Jalil would play the part of the cowardly lion.
Jalil is conflicted about his relationship with Mariam from the start. It's clear that he holds some affection for her, but he falls short of recognizing her as his real daughter. His challenge is to build the courage to accept Mariam for who she is.
So how does our cowardly lion find his nerve? Jalil, like Mariam and Laila, is deeply changed by the years of war. Jalil had been a fairly wealthy businessman when the Afghan government was in power, but the communists "confiscated… much of [his] land" once they took power (4.50.151). The years of war that follow take a toll on his family, too, causing the death of one of his wives and several of his children.
It isn't until he loses the ones he loves that he realizes how important family actually is. That's what prompts him to visit Mariam in Kabul unannounced—and that's also what prompts him to leave her a portion of his inheritance, along with a letter begging her for forgiveness and a cassette copy of Pinocchio—the film Mariam had once begged him to take her to.
Although father and daughter never get the chance to be reunited physically, Jalil's gesture shows how much he's grown since Mariam was a child. Our cowardly lion is cowardly no more.