Hey there, i haven’t posted in a long time, but well i’m back :D.
So, this is my question, is there a way to make an object that can be seen throught other objects? like, the sun flares in UDK, they can be seen throught other objects. So is there any way to do this in the BGE? And a blend would be nice too 
Sun flares are typically “camera space” in the sense that they don’t use 3D space for positioning, but instead map the 3d world to the camera view. However, It is possible to as you’re asking. I believe the only way is to simulate a “portal”, of which there are a few demos here on the forums.