I made a few changes after I've seen The Crimes of Grindelwald. Very fortunately, this will be expanded, because now there is a released new family tree (you can go see it on HP wikia).
Just a few additions, before I make the expanded family tree: M. Lestrange's full name is Manon Lestrange. The inbreeding between Corvus III and Eglantine is confirmed. They are first cousins.
In the new version, there will be a new bloodline. Cyrille Lestrange's line, who is the brother of Corvus I. Unfortunately, it end with female members who cannot pass down the Lestrange name. (Funny enough, there is a male member of the family who is not married to anyone on that tree. Is he gay or what? )
And well, it is not spoiler now, that Credence Barebone is not actually a Lestrange. But it was so close...
UPDATE - 2018.11.21.
THE LESTRANGE FAMILY TREE
So I finally made it. Used all the old and new canon info I could find. A few interesting acts of inbreeding listed from the tree:
Corvus IV and Clarisse Tremblay are first cousins.
Corvus III and Eglantine are first cousins too.
The great-grandfather of Fulcran III and Quintilla’s second great-grandparents are the same. So they are second cousins, once removed.
Also, Nozéa is Quintilla’s daughter, but also her third cousin at the same time.
Compared to the Black family, the Lestranges are even more fanatical. On the Black family tree made by JKR, there is only one case of intermarriage. Sirius Black’s parents are second cousins, but that’s all.
UPDATE - 2018 12 26
Just tiny changes. Crosses under the dead female family members, because according to the original tree, the closed flowers represent the dead witches.
And I can agree, it's pretty annoying. There's already a lot of theories on how this is possible. I hope this is not a retcon and JKR really have a good explanation.
Actually, for me, Credence's/Aurelius' character would be more interesting, if he really came from nothing. Like, you know, if he had this great power in him not because of a relation to a powerful family.
I haven't read any spoilers and I'm not following the theories on the internet, because I really don't have time for it. I hope that the next movie will bring some explanations.
These films are across the ocean from Britain, and yet using the old Harry Potter films as a crutch to rely on. 'Shock value' my arse
It's amazing to see this all on one page.
In my headcanon version of Lestranges' tree Rodolphus & Rabastan's grandfather Rivellion had a sister, Renuara Lestrange, who married Claude Rosier, so Rosier family is the most related to Lestranges from all British Pureblood families. It's interesting)
I too hope that we'll find out more about the Lestranges (and other families) in the upcoming movies. They have all the chances to tell us real interesting stories now, considering there are four more movies planned.