Do you really want a context? Ok...
this is a shaman flying on a huge bird's back, while examining the state of his cousins (other people with his abilities to speak with spirits). Usually, those cousins of his "wear" a "soul spark". But this ones wear also a "mirrored shroud"...
By the way! How would you translate "cousin"? iguales? primos? primos-hermanos?
Well, from this quote it sounds like you are reading a science fiction/fantasy novel, in which case the words' original English meanings will have been blurred somewhat.
Hence you probably can't translate cousin
because in this context it is simply the word that the author has chosen to mean other people with the ability to speak with spirits, as you explained. And a mirrored shroud
is probably a reflective cloak or veil of some description... I suspect that the literal translation given above is going to be the best you will get.