Sibling connections missing on family tree

Product: The Sims 4
Platform:PC
Which language are you playing the game in? English
How often does the bug occur? Every time (100%)
What is your current game version number? 1109.185.1030 DX11
What expansions, game packs, and stuff packs do you have installed? All of them
Steps: How can we find the bug ourselves? make 2 siblings in Cas go into world and check their family tree
What happens when the bug occurs? Siblings made in Cas dont have a line connecting them on their family tree.
What do you expect to see? lines connecting siblings on the family trees,
Have you installed any customization with the game, e.g. Custom Content or Mods? Not now. I've removed them.
Did this issue appear after a specific patch or change you made to your system? Neutral/Not Sure 

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Siblings made in Cas dont have a line connecting them on their family tree and might treat each other as strangers in game. their profiles recognize each other as family. but for instance, i made2 sims and before placing them i seperated them into 2 different households and they didnt know each other and they have no line connecting them on the tree. 

luckily though this does not appear to be allowing incest.

This does seem to be only locked to family made in cas as children born in game show their lines properly, and it also seems to only be sims that dont have a parent with them in cas. 
if you make a parent and their kids in cas the kids show as related to each other and their parents. however if you dont make them a parent they dont show as having any lines connecting them in the tree. I know there is at least one other post about this  but as it is from a full year ago and this issue is brand new for me  i thought it may be okay to post a new thing. i have tried this both with and without mods and it happens every time.