How do you cope when your child reminds you of a relative you are NC with?

[OhHolyFuck]

DS1 is very sensitive and highly strung and sometimes acts in a way that reminds me of my mother who I'm NC with
How do I cope with this?

Remember that your son and your mother are two entirely separate individuals and he is not an extension of her.

Would you be willing and able to talk to a therapist about this issue?.

You give him unconditional love and make a vow to never, ever, belittle, criticise, use sarcasm or give him any indication that he is anything but loved, cared for and the most important person in your life.
And if necessary, you fake it until you make it.
Anything less is unworthy of you...but I think you know that and I also think that you will cope with these feelings, maybe through some counselling?
Good idea to get these thoughts out and in the open where you can find ways of managing them. And some of us have been exactly where you are OP. You're not alone. You will overcome.