Billy Crudup has been a superhero in the past – you can find him glowing blue and possessing enormous power in Watchmen – and according to Variety, he's preparing to head back into that sort of world, this time for the DCEU, as he's in talks to be Barry Allen's father in The Flash.
Ezra Miller is Barry, of course, having been briefly introduced in Batman V Superman and scoring a more substantial role in next year's Justice League. Assuming the movie keeps to the lore, Crudup will be Henry Allen, who provides support to his son and works as a doctor.
Seth Grahame-Smith wrote the film, and Dope's Rick Famuyiwa is in the director's chair, having already cast Kiersey Clemons as Iris West. Ray Fisher's Victor Stone, AKA Cyborg (a fellow Justice League member) is rumoured to be showing up, though their are no real plot details around yet. The film is set for a March 16, 2018 release in the US and we'd expect to see it around the same time here.
Crudup was last seen in The Stanford Prison Experiment (which coincidentally also featured Miller) and has several movies on the way including 20th Century Women, Jackie and Alien: Covenant.