Wolf Brothers
The Wolf Brothers are the only OFFICIAL successor Chapter the Space Wolves made during the Second Founding. Leman Russ had such high hopes about the chapter that he even decided to give them half of everything the original Legion had just to make sure they would be well-off. Russ was hoping that this would be the beginning of a force called "The Sons of Russ" that would eventually form a circle around the Eye of Terror and protect the Imperium (Later accomplished by the Astartes Praeses).
Well, thing is, the gene-seed couldn't work. The Canis Helix proved to be too unstable (devolving all the initiates into Wulfen), and this, among other matters that were perhaps the machinations of Russ' rival the cyclops or his patron god, would eventually spell the end of the Wolf Brothers and the "Sons of Russ" plan. However, any survivors, if they could even be called that, would sometimes be found. In fact, Magnus actually used the failed chapter as a lesson in utter dickery against the Wolves.
Is this for the better? Depends. How sick would you be if you had a bunch more chapters doing that damn "WOLF WOLF WOLF" meme than just one?
On the other hand, GW tripped over their own fluff. The whole reason the Canis Helix became so problematic was because Leman Russ disappeared into the Eye of Terror. Before that, their gene-seed came straight from him, ensuring that the Wulfen wasn't that big of a deal. The "Sons of Russ" plan was initiated before he left, meaning there should not have been a serious issue with the Canis Helix at this time. The best part is that the Imperium's innate paranoia would result in the Astartes Praeses being founded anyway, meaning that there would be at least twice as many (probably more like thrice) chapters guarding the Eye of Terror. This would have prevented so much crap for the Imperium in the future. Welp.
