In Weedflower, Sumiko's family members are Jiichan (her grandfather), Tak- Tak (her little brother), Auntie, Uncle, Bull (her 19 year old male cousin), and Ichiro (her 23 year old male cousin). Sumiko's parents are deceased.
Weedflower details the story of a Japanese-American girl and her family during WWII. After the attack on Pearl Harbor, Sumiko and her family are eventually sent to an internment camp in the Arizona desert. Incarceration in these camps present a difficult challenge for many Japanese-Americans who are loyal to the United States. Even though Sumiko is supposedly born cheerful, she can't help but miss the flower farm in California, where she used to live with her family. Sumiko makes friends with a Mojave boy, Frank. She learns that her camp in Poston, Arizona, is situated on tribal land and that the Native Americans resent the intrusion into their area. Sumiko comes to understand that there are some parallels regarding both the Native-American and Japanese-American experience in the United States.
I assume that you are asking about the characters from Cynthia Kadohata's book "Weedflower." Sumiko is the main protagonist of the story. The story is about her and her family's displacement from their home in California to a Japanese detention camp during World War 2.
Sumiko is 12 years old. She has a younger brother named Tak-Tak. He is 5 years old, when the book begins.
Bull is Sumiko and Tak-Tak's cousin.
They have another cousin, Ichiro. Both Bull and Ichiro are much older than Sumiko. Bull is 19 and Ichiro is 23.
Sumiko has a grandfather in the book. His name is Jiichan. In typical Japanese family structuring, he is referred to as the wisest of the family.
Hatsumi her uncle, and everybody refers to him as uncle. His wife is obviously Sumiko's aunt. She is affectionately known as Auntie.