I posted this in the sports board the day it happened, but it's pertinent to your request for memories. I'll share with you my lasting memory of him and how it affected me.
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He made a post about how we treat each other- specifically the way we speak to each other. "Kill yourself" is a common, snarky response to people online and it seems to fly like water around here it seems. I thought at the time that this post it was in direct response to something severely fucked up that I said to another OKP, who I had this fucked up OKP e-fued with for a while. I went way over the top out of the clear blue and we had a new set of exchanges over it. I won't rehash that history but it was what it was and I said things I have since apologized for.

So within a day or two, Radin made a post about how it's never ok to speak death on someone or their family, for any reason. My only real response was something along the lines of the OKP mods taking the stance that it's acceptable speech to use the internet "kill yourself" retort since it's not something to take literally; it's just something people say. I understood what he said and in fact had made similar posts, but I was trying to make a point of my own instead of just telling him, "you know, you're right. Period."
I can't recall if that was the same post where he told us his grandmother was likely going to die and he had to rush to see her before that happened. I think it was a separate post but I'm not sure. Anyhow that post kinda haunts me now. I wonder if he was thinking those thoughts right then, you know?

I squared things away with that OKP and we're all kosher right today (c). That OKP's profile was previously disabled so I couldn't reach out to apologize, but it was in the initial GD post about Radin's passing that I noticed he had enabled it again, so I hit him up and we squashed it. In a fucked up way, Radin is responsible for that. Oddly enough, Radin's interaction with that same OKP weren't far off of mine prior to all this. Anyhow your brother was really just trying to talk some sense into all of us, and he was 100% correct. So my lasting memory of him will be him trying to 'increase the peace', so to speak, or at least lesson the level of vitriol within even negative interactions. He established that there is a clear line we should not cross, even in the midst of bickering, and he was right.