From Hawaii Five-0 Wiki
- Moved from New Jersey to be closer to his daughter, Grace Williams.
- Was in Hawaii for six months as a detective (transferred in from New Jersey) before joining the governor's task force as Steve McGarrett's partner. (1.01 Pilot) Has been living there a year as of Loa Aloha, presumably two by Season 2's Valentines Day episode.
- Met his ex-wife, Rachel Edwards, when she ran into his car with hers. Danny had offered her driving lessons which turned into dates before they got married. Rachel later revealed that she had done it on purpose and it was not due to being flustered at the sight of a police car, as Danny had believed. (1.10 Heihei)
- Grace Williams, daughter
- Rachel Edwards, ex-wife
- Matt Williams, younger brother
- unnamed sisters
- parents are still living
- father was a firefighter
- Dr. Gabrielle Asano, girlfriend
 Jobs and education
- Detective in New Jersey (Homicide, Sargent's stripes on NPD uniform [Ohana, Mana'o]).
- Detective with HPD.
- Joined the Five-0 task force at the beginning of the series as Steve McGarrett's partner.
- Badge number: 7576 (1.16 E Malama)
- Dresses as Santa Claus every Christmas for his daughter.
- He was shown to have torn his ACL in 1.04 Lanakila. This was written in due to the actor Scott Caan's real life injury. (Attributed to Danny playing baseball in high school.)
- Often expresses his dislike of Hawaii but has shown liking for the local food especially malasadas (1.02 Ohana) and cocoa puffs. He is also willing to take surf lessons as a way to spend more time with Grace.
- ↑ Danny: "Okay. Gracie was three, she tried to say my name, and all that she could say was 'Danno.' That's all that came out, 'Danno.'" (1.01 Pilot)
- ↑ Danny: "What is it that you do, exactly? I mean, you just help the rich get out of paying their taxes or what?"
Matt: "In all fairness, I'd like to get everybody out of their taxes, not just the rich."
Danny: "You know, people don't pay their taxes, then cops don't get paid, firefighters like Pop, you think about that?"
Matt: "Man, I'm kidding. C'mon, relax, it's the beach!" (1.18 Loa Aloha)
- ↑ Danny: "I dress up as Santa Claus every year for my daughter, Grace." (1.12 Hana 'a'a Makehewa)
- ↑ Danny: "I'm doing this because Grace wants to learn how to surf and I figured that it will be a nice thing for me to do with her." 1.15 Kai e'e