Wanda's children were younger than Franklin Richards. Wiccan and Speed are older. Has marvel ever explained how wanda's children were reincarnated before they were born?
- The case of Franklin's age is extremely weird. Basically to the point in which he has been an adult twice, but later returned to childhood. Valeria, however, was born after Wiccan and Speed. But there's actually a problem regarding Wiccan and Speed's ages, as they should've been born in 1950 (of our world, which would currently be the 1998 of the Marvel Universe) for them to have 16~ years nowadays.
- They also never really explain how they were "reincarnated". I assumed that reality was altered to make it appear as if they were the children of the Shepard and Kaplan families though they were never "born" into those families. It would explain why Speed and Wiccan look so similar despite having different parents.
- That's totally just a shot in the dark guess though.
- And since 616 uses the sliding scale timeline maybe we should just say a wizard did it. 
The sliding timescale 4 years for 1 works fine to explain the age of adult or young adults or for old-create children (Franklin should be 11,5).
I Speed and Wiccan were born at the time the original Maximoff sons were born, they should be six years old.
A few solutions:
- Marvel doesn't stick or care about its own tacit rules.
- The reincarnated twins were present even before the death of the original:
- An unconscious effect of Wanda's powers who somehow knew such things would happen.
- A conscious actions of Mephisto who like to play, and there is more games with more players (but this time not with using part of himself).
- Two poor boys were turned into reincarnated boys by Wanda or Mephisto.
- The sliding timescale isn't perfect, and it's a nightmare for explaining characters who appeared lately in the comics: My logic, the only who can work in my mind is: Thomas and William died in 1989, reappeared in 2005 at sixteen: That off-panel part followed the 1218 time-scale, in order to have children who fit enough in their own era. But since they appeared, the sliding time-scale started applying to them.
- I'd go with the "two poor boys were turned into reincarnated boys by Wanda or Mephisto." Anyways, I asked Tom Brevoort in his Tumblr. Luckly, we'll get an answer. Luckier, we'll get an useful answer.