"Sibling" items in a View?

Hi guys,

I'm really struggling with this. I've got a structure set up where I have an event type (so a rock festival, for example) which I then assign events to using an Entity Reference. This is pretty much a pseudo-category, so that I can in turn build a hierarchical experience (breadcrumb trails, URLs, etc).

I've attached an image of what I'm attempting to achieve, but imagine that under event type of festival I have, I dunno, Lollapalooza and Bonnaroo. These two are 'recommended' events under festivals (set up using a Flag), but when I'm on an event I want to display all 'recommended' events for the referenced event type. When I'm in Bonnaroo, I'll only want to see Lollapalooza. The same goes for the reverse, and when I'm on a totally different festival, I'll want to see both of the others. The attached image shows red lines as to the direction I'm trying to go.

I'd love if anyone was able to help. This is a really good module, I have no doubt it's user error but I'm just not managing to get over the finish line. Thanks all.

Kris