Speaking of twincest, we have this theory/headcanon that William and Annette Birkin are secretly siblings and possibly fraternal twins.

If that were the case it would fit quite nicely with the other Umbrella science sibling pairs, Albert and Alex Wesker, and Alfred and Alexia Ashford.

Evidence:

  • Both blond and similar look
  • No canonical information about Annette’s past
  • Other Umbrella sibling pairs
  • I just think it’s neat