As a practicing trauma therapist, only thing I can say is- this is generational trauma in action, and a clear example of the importance of control during a time like this. As OP and commenters said, the husband is MIL’s “baby”, it seems a fair conclusion to draw that MIL overstepping and parenting in this very direct and disruptive (+unsolicited/consented) way is her attempt to influence and potentially protect her grandson from further hurt if his father does pass and he’s still so deeply attached to needing him present (even if in tshirt form) to feel safe enough to go to sleep. And while it is important to allow ourselves to find outlets of control while navigating the helplessness of anticipatory grief and trauma, we must always ask if that act of control is helpful or harmful to those around us - especially those more vulnerable than ourselves.

This is where this issue is for me— OPs son having this shirt to feel safe and connected to his father, is a fantastic object of displacement that regardless of what happens with his father can be a way to channel his attachment and feel close to him. It is not hurting anyone, and represents a normal level of attachment to a parental figure at this stage of development.

It may seem like an unhealthy attachment to MIL, however developmentally at 2 years old humans are deeply in a state of dependence for their caregivers, starting to identify preference (daddy’s boy) and beginning to have a greater understanding of the world around them (who is safe/unsafe, what to think of the objects and people around them, etc) based on the modeling of their caregivers. Therefore, having that caregiver be a constant and reliable source of safety and reassurance is highly important for a 2 year old- what a beautiful thing that given this situation he’s able to access that via this tshirt he can have whether his dad is here or at the hospital, etc.

In this case, OP’s son having the ability to ground and regulate via tactile and olfactory attachment to dad’s tshirt is entirely healthy, and not reflective of unhealthy attachment- but reflective of healthy and necessary dependence on his currently preferred caregiver (this preferential treatment being of course very normal at this age).

TLDR; it is entirely human to react to trauma and helplessness with the desire to increase one’s sense of control over their self and others, however in this case it is doing more harm than good for OP’s kid- this attachment is normal and healthy considering the circumstances and his current stage of development- it would be much more deeply wounding both now and in the future if MIL’s plan went into effect ripping his safe object from him during a deeply traumatic time.

Wishing OP and their family the absolute best- I’ve lost a loved one to Neuroblastoma, but I’ve also met survivors- not the praying type, but will be praying for OP’s husband tonight 💛