So I have this very 5 level family tree and I notice some of the members were remove like my dead sim father was remove off the tree or his deceased children kids were just removed it like a problem of course I can fix it but it getting annoying having to do that

You should try the Expanded Genealogy mod by Destrospean

@kittystar72

If you use NRaas Overwatch there is a setting called "Cleanup Genealogy", which I think it was turned on by default. To turn it off, go to City Hall > NRaas > Overwatch > Immediate > click on "Clean up Genealogy", then Accept. Again in City Hall > NRaas > Overwatch > Settings > click on "Clean up Genealogy" then Accept.

If this setting is already turned off in Immediate panel click on "Total Reset" to reset Overwatch settings. Reset the town with MasterController, quit the game, clean the cache, launch the game again and then set the previous settings for Overwatch.

Also make sure you use the latest version of the mods you use!

Please note that this fixes geneaology corruption and should be left enabled, it does not break family ties at random.

It is the EA core that prunes family trees destructively.
There is a tunable, kPreservedGenealogyLinksForLivingSims, which is only set to 3 by default. Increasing it may resolve the issue, but I cannot guarantee it - especially if OP doesn't have a custom StoryProgression mod suppressing the EA management of such things.