Board Thread:Questions and Answers/@comment-1620907-20151127200839/@comment-24909831-20170810133816

Yes and no. Primaris marines' geneseed is derived directly from the Primarchs' geneseed (at least so it is presented in Dark Millennium). But yes you can. Half of the Primaris marines (of which there were tens of thousands) were formed directly into new chapters and the rest of them were formed into chapters during the Indomitus Crusade, last one being (apparently) Wolfspear which chapter world was set next to the Pit of Raukos. The Primaris marines were also recruited 10K years ago, some of them retaining memories from their birthworld, most notably Ultramarines' Captain Felix, but apparently some others too at various degrees, which means that Primaris from Russ' lineage are true Fenrisians. At least the first generation is.