[SPOILER] Alexander von Brennenburg...

[Alardem]

Does Daniel even fit as a great uncle of an adult man age-wise? I'm trying to figure out how old he and his sibling would have to be by 1899 to make it possible...

Hell yeah. TDD is in 1839, 60 years (and a couple of generations) before Mandus' time.

We also know that Mandus Co. has been around since 1828, which would imply that either Oswald's father or grandfather had started the company. We don't know anything about Oswald's age, although his children are apparently 9 years old (Lily was buried in 1890) so I'd assume he's in his 30s or 40s.