in a bunch of interviews capcom revealed that if DMC5 did go ahead it would reveal that nero is Vergils son. it makes sense in a way if you send dante to his late 30s/ early 40s and asume the thing that happened a "year" before DMC3 was Vergil loosing his lover and child then it fits. but thats just pure speculation on my part
Um, please reference and link these interviews, since Capcom and Kobayashi, during the intial reveal trailers, stated that Nero was not immeditaly related to the Twins, meaning he was neither a lost brother or son to either of them. that leaves him as a distant descentent of Sparda from a previous child, or Sparda himself reincarnated, which is the more likely theorum since his story paralells Sparda too much for sheer lucky. One of the major plot moment of the game, when Nero saves Kyrie and the end, has a piece called "SPARDA'S WILL" when he kills Sanctus.
Also, Dante is verified 29 in DMC4 as he was 28 in dmc1, and 19 in DMC3, and DMC4 is a year later. Istuno and Kobayashi state dthes in inverviews concerning time frames