The show Hawaii Five-0 has many memorable characters, and those characters certainly come from diverse backgrounds. Those diverse backgrounds produce plenty of family members, good and bad. Steve's mother, Doris, isn't exactly his best relative, given her tendency to manipulate him and lie about important things, which frustrates Steve to no end.
Danny's brother Matt isn't the best relative either, but Danny does have a good relative in his nephew, Eric, who greatly improved his life's direction with Danny's help. While the Five-0 characters have relatives capable of murder, lies, or getting into trouble, they also have family members that are there for them always.
Best: Isabel
Jerry's younger sister Isabel pays Five-0 a visit in Season 6. She's smart, funny, and obviously close with her brother. The two reminisce on childhood memories, and as the episode plays out, Jerry discovers that his sister is involved in the theft of an elephant.
However, she has a good reason, as she wanted to save the elephant from its abusive environment and send it to a better home. Jerry ends up helping her, alongside Eric, Max and Kamekona. Isabel, despite the risk, did what she felt was right, and stood up for what she believed in.
Worst: Mary
Steve's younger sister Mary was introduced in the first season, and was shown to be troubled. Steve helps her out of jams several times, as he rescues her from kidnappers and clears her of being a diamond smuggler, for instance.
However, as the series progresses, Mary adopts a little girl and becomes more responsible and mature. Still, she does tend to lean heavily on Steve for help and advice, and doesn't always return the favor.
Best: Koa
Tani has always looked out for her younger brother, Koa; especially after the death of their father. Koa is sweet and grateful to his sister when she offers her help to him and defers to her views on important matters. The two share a close bond.
In the show, Koa goes out of his way to help others and puts his own hard experiences to good use, showing his selflessness and kindness. He even goes out of his way to check on one of the people he's helping in a Season 9 episode, and Tani aids him in his efforts.
Worst: Michael
Michael Noshimuri was obviously bad news from the start. He's nothing like his brother, Adam, who genuinely wants to legitimize the Yakuza and end their days of criminal activity.
Michael was not too happy with Adam's plans, and instead creates major problems for both Adam and Kono, especially when he frames the latter for murder. Michael wasn't the best brother.
Best: Eric
Eric Russo is the nephew of Danny, also from New Jersey, and initially, a mouthy kid making bad choices. Eric's reckless behavior gets him sent to Hawaii by his mother, who hopes that Danny can straighten out his nephew.
From the time he's introduced in Season 3 to the end of the series, Eric changes for the better in a big way, as he ends up turning his life around and working for the crime lab. He even helps out Five-0 on their cases on a few occasions. He's funny, and he's also a good friend.
Worst: Gabriel
Gabriel was Chin's brother-in-law, and a big-time bad guy. He was one of the most significant villains that the Five-0 team ever faced, especially in Chin's case. Gabriel is the complete opposite of his late sister, Malia, given his brutal tendencies and criminal activity.
He's even revealed to have killed Chin's father years before. Though Gabriel cares for his daughter and sister, and has a heart-to-heart with Chin prior to his own death, it doesn't erase all the bad he had done and the pain he had caused over the years.
Best: Malia
Malia was the girlfriend, and later, wife, of Chin Ho Kelly. She and Chin broke up for a bit when HPD accused Chin of being a dirty cop, and Chin broke off their engagement to protect her.
However, they ended up back together and married; their love was strong and true, and they were incredibly happy together. She was tragically killed at the end of the second season. However, in her time onscreen, she was always supportive and caring towards Chin, she was kind to everyone, and she tried to help Kono when she had her badge taken away.
Worst: Matt
Danny's brother Matthew was a stock broker, and he committed some serious fraud and dealt with dangerous people in order to cover up his losses. Unfortunately, Danny finds out from the FBI just what Matt's up to, and he desperately tries to help his brother.
He urges him to stay so that they can face everything together, but Matt makes the heartbreaking choice of leaving anyway. Later, Danny learns that Matt has been murdered, further causing him pain. Matthew's selfishness and bad choices led to some devastating consequences, of which his entire family had to live with.
Best: Aunt Deb
Steve McGarrett's Aunt Deb is the sweetest. She truly cares for both Steve and his sister, Mary, the latter of whom she raised after Mary was sent away from Hawaii by her father. Deb is a talented singer, and selflessly gave up a promising career in order to raise Mary. She visits Steve a few times in Hawaii; on one such visit during Thanksgiving, she tells Steve that she has a brain tumor.
Nonetheless, it doesn't stop her from living her life, and she later gets married and, with help from her family, crosses things off her bucket list, including driving a police car at outrageous speeds. Sadly, she later passes away, but Carol Burnett's Aunt Deb was definitely the best, and exactly what Steve needed, considering the rest of his family was pretty dysfunctional one way or another.
Worst: Doris
Doris McGarrett wasn't exactly a candidate for "Mother of the Year." She faked her own death when Steve and Mary were just kids, and she subsequently missed out on a significant portion in both of their lives. Plus, she left her husband to try to solve her "murder," which he worked all the way up until he died himself.
She wasn't fair to her family, and even after Steve found her again, she wasn't honest with him, and she often lied to and manipulated him. She didn't even stick around for too long after Steve discovered she was alive, again leaving her family without the opportunity to mend their relationships with her or to spend time with one another.