Again, we're sticking these two old geezers together as one character. Even though they didn't exactly stand by each other all their lives, we're certainly not going to tear them apart now.
We've never seen a guy so excited to have a grandson. This is Naomi's maternal grandfather, and when Stephen was born he was beside himself with happiness. Grandpa is a retired doctor, but despite his health and age he comes out of retirement to care for sick people in the internment camps.
We don't think that Grandma and Grandpa Kato had a good marriage, since Grandma would often leave him and go to Japan with Naomi's mother. But he must've at least been an okay dad, since he raises Aunt Emily all by himself. She turned out okay, right?
He dies of a heart attack after overworking.
Naomi's maternal grandmother is unshakable in her grandchild's memory. She remembers her as her bathing partner and as a woman who could endure anything. Unfortunately, Naomi was wrong. Grandma Kato survives the Nagasaki bombings. But her memories haunt her so much that she has to write a letter to try and relieve her sorrow. We don't know if it works, but it certainly helps Naomi reconcile with the memory of her mother.