Complex sentence: The Silver Fang, Fianna, and Get of Fenris are among those who especially value heritage; in these tribes a young Garou wouldn't be allowed the proper rites and trails to join the tribe if he wasn't of appropriate heritage.
Split into simpler sentences: The Silver Fang, Fianna, and Get of Fenris are among those who uphold heritage very much. In these tribes a young Garou wouldn't be allowed the proper rites and trails to join the tribe, if he wasn't of appropriate heritage.