So… If a players has a ghoul settler, my question is do feral ghouls attack them?
I have a player who is very keen to play a ghoul (Its the closest she can get to a zombie in the fallout world) 
lets jut call it an obsession.
I am curious what everyone else thinks would happen? Would they recognise a fellow ghoul?
There are a couple of examples in the video game.
(Note, I stole this answer from someone else on Quora, so credit to them for doing the legword).
Here is the meat of the text for those who don’t want to trust the link:
Q: Do feral ghouls ever attached regular ghouls?
A: Yes, they do, but only if they’re attacked first.
The evidence lies in Fallout 3, with the ghoul Roy Phillips from the Tenpenny Tower quest. Now, during the quest, the player is tasked with breaking Roy Phillips and the rest of the ghouls into the Tenpenny Tower. Well, to make a long story short, in the end, if the player is successful, Roy Phillips rewards the player with a unique item called the Ghoul Mask, which stops the feral ghouls from attacking the Lone Wanderer.
Another instance we have is from Fallout 4, with Theodore Croup, a ghoul who along with his family, succumbed to the deadly radiation from the bombs, however, Theodore’s family got the worst of it and turned into ferals. We learn through his entries, that his feral family didn’t attack him, and for 200 years, Theodore tried to teach his family how to be normal again. It wasn’t until out of frustration that Theodore attacked his family of feral ghouls, which resulted in them attacking back and killing him. Here are Theodore’s entries about the whole ordeal.
Journal Entry: 1/15/78
When my father said that nothing could change the “Croup Family Dynasty,” not even the crippling debt from a bad stock market trade, he apparently didn’t think about a world flooded with radiation poisoning…
Let me back up. When I watched the mushroom clouds rising, I thought that it was someone’s sick joke. I’d prayed for something to wipe away the debt, but this was not what I had in mind. But I’d take a blue-collar lifestyle over having the majority of my facial features slide off in my sleep…
Journal Entry: 2/2/78
Well, could be worse. I locked the rest of the family in the basement and hid the key. Couldn’t bring myself to kill them. They may be disgusting monsters, but that’s still my Aunt Belinda in there.
I’ve started to find that there are other survivors out here. Some of them look like roadkill, too. They all killed the ones that turned into monsters and started trying to kill us normal ones. Weird thing I noticed, none of the ferals seemed interested in attacking those of us falling apart.
Journal Entry: 2/10/78
Ok, it worked! I went into the basement and the rest of the family didn’t try and kill me! Actually, they kind of ignored me, but that’s not the point. The point is, the old world is dead, everyone is back to square one. Our debt is gone and we can start over! Look, if I can still talk and function and act like a normal human being, then so can they. They just need a little nudge. The Croup Family will be back on top in no time!
Journal Entry: Who cares?!?
Hundreds of years…
HUNDREDS!
I can’t ■■■■■■■ die. None of us can! I’ve spent hundreds of years trying to teach these creatures how to act human! I’ve got nothing to show for it, except maybe my cousin James can spot the difference between a salad fork and a regular fork. I can’t be sure he’s not lucky.
How the hell are we supposed to be the affluent socialite Croup family again if we’re all monsters?? This is pointless. I swear to God I’m going to bust Aunt Belinda’s head if she doesn’t listen to me. You just watch!
Thanks @Candyman that does give me something to work with. I like the idea of an intelligent Ghoul being able to move through groups of ferals unless they are attacked, also give me some interesting options, if the situation does crop up…muhahaha 