, as he is I am not going to be accepting Fenrisson. I need his background expanded on a bit more for starters.
I get the idea that he was without a family since they were killed, but what happened? How did he learn to survive? Why did he not stay with his tribe/clan? If he was alone/mostly alone for a period of time than how was he able to be chosen?
Has he done or been part of anything notable since becoming one of the Relictors?
As for becoming a member of fifth company, my answer is no on that one. The reason that all members of the respective squads are relatively close in age is because they started as scouts together. So Fenrisson won't have recently met the likes of Seccarin, he will have known him and fought beside him for decades.
So sorry, but the background of him being a scout sergeant needs to go.
Also keep in mind that three years prior to this RP the Relictors chapter was declared Excommunicate Traitoris for their use of daemon weapons despite censure by the inquisition in the past. When this happened the chapter was shattered by the Grey Knights and the remnants fled. It was at this point that Laendro Tatecen, a member of the chapters librarius, took command of remnants of the chapters fifth company and fled the conflict. At some point in those three years Laendro and the marines under his command learned about the Grimoire and have been seeking it out.
Thats the gist of where the characters are at present; seeking a powerful chaos artifact, hunted like traitors, and without backup or support. For all these marines know, they represent the last of their chapter.
Now the reason why all of the characters in either of the to given squads will have similar ages and have been scouts together. This allows you guys to create better interactions with one another. If you've fought side by side for fifty years, there is a chance that you know when one of your own is troubled, or that you do not have to go to great lengths to explain a plan in the middle of a firefight. The hardest part of team character building, the introduction, is partially done for you.
So please rewrite that background, and keep in mind that Fenrisson will be in power armour and will not have access to a sniper rifle.
And for those who want/need it, here is most of the information currently available for the Relictors.