#Wikidata, it should be obvious; there is no single language that is to be preferred as a source. Philosophically the language best suited to provide a source is a source that is closest to the events or the persons involved.
When the subjects are historic like the "Sanjak of Bosnia", many of the facts involved are not clear; the family name of the first sanjak-bey may be either Hranić or Pavlović. It matters in that the understanding of history may depend on it.
One reason why there are so few sources in Wikidata is because it is so cumbersome. The sources and their author have to have a Wikidata item in their own right.. It would help if just an ISBN or ISNN number would suffice..
Reproducing a family tree for Mr Isa-Beg Isaković is possible but it does not make sense to do so without information I trust. With a subject related to Bosnia and the Ottoman empire, I prefer to leave this to people who are knowledgeable.
What I can do is build the succession of all the sanjak-beys that ruled the Sanjak of Bosnia. My source would be the English Wikipedia article and it does refer to several red links. Including these will help link potential articles into this framework and in a way it can make Wikidata a source for Wikipedians.