no they have at least 1/2 of chapters are descended from the ultra marines. The Storm crusader successors are attucally their compaines which have split off into different quadrants of the gaxaly forming new chapters and still fighting in the name of the storm crusaders. But having different formings, names, company markings, but they are known by others as the successors. but this is not true because they are not successors they are 50 chapters yes but they are not like massive thing. Lets just say this would happen is very unlikely plus this the first time in 10,000 years so its just the storm crusaders going into the eye of terror whats the harm of that they'll probaly all die.
