Not sure this is a relationship setting bug or something else

I've done what you suggested on MC Commander but didn't work. Am I allowed to upload the MCC menu here? Just let me know it's illegal, then I will delete them. 🙂

@daikoyuHow can I do that? Could you help me how to do? Thanks.

Your problem is not your female sim, but your other sim J.

I think J-family tree is so yes? (screen 1)

You need to make that his family tree is so (screen 2) 

<remove Screens>

@daikoyuI prefer the vanilla way if there is, but it will be sad if I delete their previous parents in family tree. ☹️ Anyway I already removed MC Commander. Usually I don't use it. But anyway, I'd love to learn the way of removing the family tree. No worries. I can wait until you are free. 🙂

This is SimX, he has a bad relationship with his parents, and will no trace from them in his tree.

<Remove Image>

We load SimX in CAS and remove SimA and SimB.

<Remove Image>

We save SimX in my library.

<Remove Image>

Now we leave the CAS, without saving and use cas.fulleditmode.

<Remove Image>

Now we should have two Options: First we remove all trace or we replace it.

First replace it: SimX want a witch family so i use my Witch-family and go there in CAS.  We load the CAS and add Simx from my libary. Now you can set the relationships there and this is now his family tree. (Mother A, Mother B, Sibling B)

<Remove Image>

Remove the TREE!

First use cas.fulleditmode now i load my Witch-family again. I add SimX to the family but let the standard settings.

<Remove Image>

Now I can split the household and this version from SimX save in my library/gallery. He should now always have no family tree if I place him in my world. 

(This Sim a precious for me, so I delete the images.. had should use another Sim for)

Ah, now see it, maybe you could use MCC for it. After you delete your Relationship with SymbolSim you can maybe use under MCC-Relationship Add Relationship or Set Active Relationship for Lot… I know MCCC in Sims 3 you can add Siblings in this way, or maybe sims 4 Set Family Relationship Mod can help you? (google it, is a mod from simsmodelsimmer)

And yes, without lose your family tree, you cannot restore the sims to sibling status. Is sadly so works vanilla.

@daikoyuYeah I know you can always add or remove family in the sims 3 with NRaas MC mod.I tried the sims 4 set family relationship mod but it's more for expanded relationship such as uncle, aunt, parents in law or great grand parents something like that. No worries. 🙂 If there's no way, then I'm ok to play them as friends. I wouldn't have the chance to learn this system without you. I appreciate you. 🙂

[update]

I removed all images as they are not my sims. Hope everyone here  understand this. :-)

[Update]

I made the 2 sims to siblings using MCCC. It was so easy. I didn’t have to delete the relationship between them. I simply chose ‘add relationship’ on mccc menu.  Thanks.