CK II - 3.0 Post parent death children born wrong dynasty

[Raga-Zun]

One line summary of your issue
3.0 Post parent death children born wrong dynasty

Game Version
PXTU

What expansions do you have installed?
All of the above

Do you have mods enabled?
No

Please explain your issue is in as much detail as possible.
My grandson who was my heir died a few months before his only son, my great grandson, was born. My great grandson was given the dynasty of his mother, as the game gives the mothers dynasty if the father dies before they were born. You fixed children born after their dad's death from being bastards, you however didn't fix them being a different dynasty.

Steps to reproduce the issue.
Via cheats get your son to marry a noblewoman and impregnate her, kill your son, when the child is born it will be her dynasty.

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[Chunakun]

Had the same problem. somehow the game changes the marriage of the parents to matrilineal if the father dies before the birth of the child.