After married sims die, why are they not considered married in the family tree anymore? That is after they die... Must they die together or something? Is there a cheat to modify the relations in family trees? Pls reply soon..

That's just how the game is designed. Ever heard of "till death do them apart"?

The simple answer is that it gives the widow or widower the option to remarry after their spouse has died. Imagine how hard it would be to get a divorce from a ghost.

You can try google and search for some mods or hacks, but there probably won't be any. At least the children's family tree still shows who their parents are, right?

ooo... ok.. Cos I saw the ancestors of the goth family are still linked after they die. So i thought it was supposed to be like that.. Btw, ty..

I think that's because the creators already linked everything before the game got released. Perhaps you can use SimPE for that.