Sung that's a bit how I feel when people innocently give me presents; I want to wail, but I've just got rid of my favourite mugs and now you are giving me more cr**p. The thing is, it is not their fault, it is genuinely a present, sometimes I think the point of throwing stuff away is to be able to genuinely appreciate it when people give you something they have chosen and want to treat you with.
However, family members passing on "treasures" is not actually a gift at all. They are just avoiding dealing with the decluttering themselves by forcing you to make the decision. So unfair. If they really believe the object is of great value, they should either keep themselves, sell it, dispose of it, or ask you whether you actually want it. However, this is something that might have to be tackled slowly and gently rather than reacting to objects as they come in. Maybe just say in advance, what a kind thought, unfortunately we don't have room for that/we are making our own memories etc.
When someone gives you a present/treasure you don't want, I think there is a limit to how much time you need to live with that "present". make it clear that a treasure might be sold in the next year or given away, in which case do they still want you to have it? Imagine if someone gave you a box of soap you were allergic to and forced you to use it, no you'd would probably think you were justified in giving it away to someone else.
On the other hand I do have a friend who is obsessed by removing clutter to the extent it is controlling, and who actually will not accept gifts of food or drink because there is no "room" in her fridge cupboard for them. And this stems from her own bad experiences with a mother who was incredibly cluttered and her desire to remove herself from this past life - I think you have to really work through issues to see things clearly and distinguish very violent reactions to "stuff" (other people's stuff which you cannot control) from normal sensible reactions to having enough and no more. Same friend is strangely keen on giving other people presents too, it is as if the patterns than affect her own household management do not stop her wanting to buy stuff like her mum did, only she then gives it to other people.
Today I am working through the kids school books, finding lots of lovely things to keep, but throwing a mass of non important "paper" bits of exercise books that weren't used, maths books, boring bits of science books. It is such a wonderful capsule of memories to read their school books from ten years ago, I will definitely keep a pared down version - I think it is for THEM, not just me.