Marty Lee is Henry's college-aged son and the only family Henry has left now that his wife has died. Even though Marty and Henry love each other a lot, they still have some issues communicating properly; both can get tongue-tied and awkward around each other:
The lack of meaningful communication between father and son was based on a lifetime of isolation. Henry had been an only child, without siblings around to talk to, to share things with constantly. And Marty was the same. Whatever stumbling methods of communication Henry has used with his own father seemed to have been passed down to Marty. (13.2)
But even though Marty often misunderstands and fights with his father, in the end he loves Henry and wants his approval and blessing very much. That's why he comes around to visit Henry regularly and why it's so important to him that Henry likes Samantha, the girl that Marty has fallen in love with.
Like his father, Marty definitely falls hard when he falls in love. He's nervous about introducing his father to Samantha, who is a white girl that Marty met in college, but is also determined to make his own choices without letting any traditionalist views get in the way. He brings Samantha to meet Henry; he's proud to show her off, even though he's nervous about his father's reaction. When Henry reacts positively, Marty is relieved and surprised:
Henry pruned a small branch and tossed it in a white bucket. "I like her," he said to Marty, loud enough for her to hear it. "You did good."
"I'm glad you approve, Pops. You know, you surprise me." (19.30-31)
This stands in stark contrast to Henry's father's reaction to Keiko, doesn't it? And it's a good thing, too, since Marty is completely devoted to Samantha, so who knows how he'd respond to fatherly disapproval. Perhaps, like Henry, he'd be willing to risk never having a relationship with his dad again in order to remain loyal to the girl (okay, more like woman in this case) he loves. When Henry sees his son and his future daughter-in-law interacting, he knows that Marty will be okay—and unlike his own dad, this is all Henry needs to give his blessing to their union. Lucky Marty.