I'm not speaking on their behalf, this simply my own opinion.
I think that they are absolutely convinced that Jeremy is guilty and that he is exactly where he should be. So there is no benefit to them to fight for the release of anything, there is no incentive and there is nothing for them to gain. They also do not have the power that people think they do.
It's also worth noting that if new evidence is released to show Jeremy to be guilty that was not originally used by the prosecution, then it can't be introduced now. Where as if evidence favourable to the defence is uncovered, then it can be introduced via the court of appeal.
Rightly or wrongly, I'd imagine that the relatives have no desire to assist Jeremys cause in this way. I don't see why that is not understood.
It works all across the board, it's the same reason why if I see something which supports the defences case, I'm not going to go out of my way to bring it to everybodies attention (although I've done more than most), likewise if Mike or one of the other supporters of Jeremy notices or sees evidence which looks bad for Jeremy, then they're not going to put neon lights around it.
It's a clever answer Steve. But it doesn't wash with me. Not in the slightest. Not want to assist Jeremy's cause? No incentive and nothing to gain? I think I'll use your own reasoning of late and turn that around to 'plenty to lose'. They are labouring under a weight of suspicion regarding fabrication of evidence, collusion, perjury and perverting the course of justice. Standing foursquare behind EP's game of concealment is hardly the moral high ground is it? They must be well aware of the issues in question. They could speak up in the interests of openness as opposed to concealment. They do not a do so and the message that sends out is not good one.
I'm not trying to be clever, I don't expect they're interested at all, as far as they are concerned the correct man is in jail. There is nothing which is an incentive for them to take any action, and as I say what power is it that you think they have anyway?
I also think that your descrption of them being under a weight of suspicion isn't particularly accurate, okay, perhaps that's the case with the members of this forum, but not in the real world, in the real world it's the complete opposite and supported locally very well.
I don't really know how to explain it any better other than to put yourself in their position, would you go out of your way to assist the person who you believed killed your family? I don't know perhaps you would, but I know I wouldn't.