1940 Jay Garrick inhales heavy water fumes and gains super speed. Becomes first Flash.
1948 Jay Garrick and Joan <> marry.
1952 Jay and Joan Garrick discover they cannot have children, apparently because of the heavy water accident that gave Jay his powers. An attempt to adopt ends badly.
1955 Jay Garrick, wife Joan, and entire Chicago suburb of Keystone disappears. No one remembers it ever existed.
1958 Barry Allen is caught in shower of different chemicals hit by lightning. Becomes second Flash, calling himself that from subconscious memory of original.
1960 Wally West, 12 year old nephew of Barry’s girlfriend Iris West, gains same powers from similar accident. Is called Kid Flash.
1961 Flash (Barry Allen) accidentally breaks vibrational barrier holding Keystone in stasis. Fiddler, Shade, and Thinker caused the disappearance and stasis and are looting the city. Barry Allen helps Jay Garrick defeat combo. Barry offers to change name entirely but takes name of Flash II at insistence of Jay Garrick, who is honored to have someone take his name and thinks of Barry as the son he can never have.
1962 Both Flashes save members of Justice Society from Vandal Savage and JSA decides to start up again
1970 After many delays, Barry Allen and Iris West marry.
1972 Iris West Allen gives birth to twins, named Don and Dawn.
1975 At age 27, Wally West adopts name Flash III with blessings of Barry and Jay.
1976 Wally starts affair with the new Wonder Woman while they serve with Teen Titans.
1977 Cassandra Troy is born to Wonder Woman II.
1980 At tender but very precocious age of 8, Tornado Twins join teen heroes in the New Teen Titans.
1984 First independent case of the Tornado Twins, aka Don and Dawn Allen
1985 Martian Invasion/Secret Crisis. Barry Allen dies heroically. Wally West reveals identity to world and swears to uphold the name of the Flash.
1988 Wally West marries Linda Park
1990 Birth of Iris Linda West
1995 Tornado Twins split. Don takes name Kid Flash despite his age of 23, Dawn takes Impulse as a nom de hero.
1996 Marriage of Dawn Allen and Victor (Cyborg) Stone
1997 Birth of Jenny Stone
2003 Jay Garrick is mostly retired, attending occasional meetings of the JSA and occasionally helping others when needed. He is still in excellent health for a man in his mid-80s (or late 70s if you take into account the six-year stasis Keystone was in).
Wally West at 54 is the person most people think of as the Flash. His daughter (called Irlinda by family and friends) is showing signs of super speed abilities.
Don and Dawn Allen revealed their identities when Dawn married Victor Stone. Don seems to take a very cavalier attitude toward his heroic ID and is somewhat estranged from his cousin Wally. The fact that he has taken Wally’s place in the Titans may have something to do with this. According to the tabloids, Don has also apparently had flings with every unattached super-powered/costumed female within 15 years of his age (either direction), and the tabloids are only half-wrong.
Dawn is closer to her cousin Wally and, despite her chosen hero name, is fairly responsible. She has also scaled down her superhero activity to take care of her little girl. At 5, Jenny is starting to show signs of superspeed abilities, too. Don and Dawn seem to be just as fast as their father and cousin, leaving one to believe that one either has or doesn’t have the connection to the Speed Force.
Iris Linda (Irlinda) West has made a couple of appearances as Tornado Kid. She often baby-sits for her second cousin Jenny.
Wonder Girl II is commonly thought to be the daughter of Wally West and Wonder Woman II, and common wisdom in this case is correct. She seems to have inherited the family connection to the Speed Force.