The history of Henry and Nora Allen (best known as Barry Allen’s parents) can be a bit confusing thanks to a long history of retcons. For those new to comics, a retcon is short for “retroactive continuity”, and refers to the changes inserted into a character’s or an event’s history by later writers. Here’s an explanation of the elder Allens’ histories to date, with an emphasis on their interaction with the Rogues and other Flash villains.
Henry was a country doctor, but the couple went to another doctor to give birth because Nora was expecting twins. Another woman, Charlene Thawne, gave birth at the same clinic on the same night. Unfortunately the doctor was drunk and allowed the Thawne baby to die, so he gave one of the Allen twins to the Thawnes and told the Allens that their other baby had been stillborn. The child that the Allens kept was Barry Allen, while the other twin was raised as Malcolm Thawne. The Thawnes were abusive grifters and Malcolm grew up unhappy and bitter, ultimately to leave a legacy of hate as Cobalt Blue and through his many descendents.
Barry grew up thinking he was an only child, and had a happy childhood. Eventually he became a police scientist and the Flash, and his parents lived a few hundred miles away. He didn’t interact with them often but they all seemed to have a good relationship, and they attended his wedding. They didn’t learn he was the Flash for quite a few years, however.
The Top died partway through Barry’s career as the Flash, which was an unforeseen consequence of their battles. His angry girlfriend, the Golden Glider, targeted Barry’s loved ones in revenge, including a strange attack on Barry’s wife and parents which left them seriously ill. He was able to save them, and she didn’t bother his parents again for unknown reasons.
Barry’s wife Iris was murdered by Professor Zoom not long afterwards, in a storyline which didn’t involve the elder Allens. But Professor Zoom’s real name was Eobard Thawne and he was from the 25th century; he was a descendent of Henry and Nora via their son Malcolm.
Sometime later, Henry and Nora were driving to visit Barry when their car was struck by a careless driver. Nora was left comatose, while Henry had a heart attack and died — but he was seemingly revived right away. In truth, the Top’s ghost had possessed his body and lived in it for weeks, although this was kept secret from nearly everyone. ‘Henry’ even lived with Barry while Nora slowly recovered from her injuries. Eventually Barry was able to trick the Top’s ghost into leaving his father’s body, and Henry’s soul was able to re-possess it. Left no worse for wear, Henry and Nora continued their lives until soon afterwards attacked by the Top in another attempt to frighten Barry. Barry successfully dealt with the Top and he no longer harassed the family.
Life went on. Barry tried to marry again, and his parents were present at the wedding. But Professor Zoom attempted to murder the new bride as well, and Barry broke the man’s neck in front of everyone while saving her. Barry went on trial for murder for a very long time while his parents watched anxiously, supporting him through all the hard times (including when his face was pummeled into pulp and reconstructed to look like a stranger’s, all to keep his identity secret). Ultimately he was acquitted, and went into the future to live with Iris after learning she was alive. Henry and Nora were left behind in their own time period, and quietly outlived their son because he died soon afterwards in Crisis on Infinite Earths. They died not long after he did, however, and their graves were located next to his public monument.
And then things got really weird.
Like many comic characters, Barry eventually returned from the dead. But his life and history had now been radically different. Now Nora had been murdered when he was a child, and Henry had been convicted of the crime and died in prison. Professor Zoom, aka Eobard Thawne, had gone back in time to kill her (his own ancestor), thus changing Barry’s entire timeline from that point on. No longer had Barry enjoyed a happy childhood, and no longer had the Top ever possessed Henry’s body. Some events — such as the killing of Professor Zoom and the trial — presumably still happened in some way, but they didn’t quite play out the same. Despite this, Barry was still mostly the same person, just more driven and somewhat sadder. But eventually he made a catastrophic mistake.
Having learned that Professor Zoom could change history for the worse, he decided to change it for the better by attempting to undo the murder of his mother. But while Thawne had a great deal of experience with changing time, Barry was far less knowledgeable, and he created a vastly different reality (known as Flashpoint). Though Nora was alive again, the Flashpoint world was horrible and had to be undone. Barry and others succeeded in repairing some of the damage to the universe, but the world was still left radically altered (which we know as the New 52), and that brings us to current comics continuity.
Nora was still murdered in the history of the New 52 universe, and Henry is alive and in prison for the crime. The identity of the culprit is unknown to us, however, and it’s also not known if Professor Zoom still exists. Eobard Thawne has been mentioned as a scientist in the future, but it’s not clear if he’s ever been Professor Zoom. And Barry was raised by family friend Darryl Frye, the chief of police. It was strongly implied that Frye and Nora had an affair before she was killed, and that she was on the verge of splitting up with Henry.
You can see some familiar elements here if you’ve watched the current Flash television series, like the murder of Nora and imprisonment of Henry, and Barry’s police officer father-figure. The obvious implication has been that Professor Zoom (aka the Reverse Flash) committed the crime on the show too, but we’ll see if there’s a swerve which might turn out differently than the comics. After all, the show has a lot of different histories to play with.