Sonja Tannhaus is Marek Tannhaus' wife, Charlotte's mother, and H.G. Tannhaus' daughter-in-law.
In 1971 in the origin universe, after her husband got into a heated discussion with his father, Marek promptly gathered Sonja and Charlotte into their car and drove off. Unfortunately, the family was involved in a car accident that night that led to all their deaths.This in turn resulted in driving H.G. to build a time machine that ends up splitting the origin world into the two separate realities that Adam and Eva recognize as their own.
In what is referred to as the paradise universe, however, the family is stopped on the road by Jonas and Martha, who convince them to turn around, subsequently preventing the family's death and thus preventing the origin world from splitting in the first place. On returning back to her father-in-law's place with a calmer Marek, she explains to H.G. that Marek thinks they ran into two angels on the road.
Sonja is an anagram of Jonas.