Hi guys! I told before that this week I would entirely working on God Guardian mod but suddenly one of my twins had been diagnosed with a cancer (from Healthcare Redux great mod). So I've got inspiration and currently working on addon for Adeepindigo's mod.
So with the addon after a sim is diagnosed with a cancer or serious disease like malaria, meningitis or tuberculosis their twin with a some chance receives anxiety moodlet that something happened and they should talk ASAP.
So in deep thoughts category there is an interaction to ask if something is happened. This causes a sick sim to reveal their medical condition – and that hurts both of twins.
When a sim knows about their twin medical condition they can support them:

So that's how it is for now ;) I'll be happy with your feedback and ideas regarding this add-on!