Fluff : The Angels Sanguine and the other Imperial Organisations

As all heirs of Sanguinius the Angels Sanguine are a loyal chapter in the eyes of the Emperor. The relationships of this noble chapter and other loyal imperial organisations are excellent and many commanders regard the Angels like saviours in many occasions.
The Angels Sanguine have participated in many campaigns in tandem with the Dark Angels , Black Templars , Ultramarines , Space wolves and other Chapters. Indeed an Angel Sanguine Astartes is a warrior you want alongside you in every situation.
But no Chapter, no Company, no Brother, is more welcome than a Blood Angel. The Angels Sanguine more than often are participating in requests for help with their noble primogenitor Chapter not like a little brother seeking to gain the respect of the older sibling, but like a blood brother seeking to help itheir family in times of need. Ultramar, Armageddon, Siege of Corinth, are some of the Battles that Brothers of the same blood but in different colours fought side by side spilling their blood in the same mud.
This bond of Brotherhood between Blood and Sanguine Angels has caused a strange tradition. Battle Brothers of both chapters to exchange shoulder guards after the complition of succesfull campaigns. The strange part of the tradition is that the Machine Spirits of both armours are rejoicing at this exchange and treasure the new part like their own. The techmarines of the chapter cannot explain it still and they call t--his Tradition ''Same Blood , Same Armour''.