I wouldn't be worried about mental damage. :)
Likely he is mounting. also, he's probably VERY sensitive to your moods right now, and considering what's happened in the last few weeks, he's overloaded on stress. I wrote up a social paper and placed it in the health pages on cat behavior that may give you a better understanding of Luffy's behavior. True, it's about adding family members, but it applies just as well to subtracting family members as well.
You'll have to treat him like what he is; a kid who lost his siblings and is upset becuase his parents are acting upset.
I'd suggest removing all the breakables or placing them out of reach, and then just riding it out. normally a cat will adjust to losing a family member in a few weeks, but it also is effected by the length of time the humans are in mourning. Once he senses your own stress levels are down and things are back to normal, he'll adjust and cope.
I think Savas said it all. Luff is reacting to your mood and the loss of his siblings. Behavioral changes in the presence of stress, death and discomfort is not uncommon. He misses Pen..a lot. It just happened, and not just once but twice so you're going to have to give him time to heal. He'll bounce back in a jiffy, I promise. Cats heal way faster than humans, and are able to adapt to new environmental conditions. He'll get it, don't worry. Try not to act upset towards him because then all you'll get is a frightened cat who is disoriented and doesn't know where to go or what to do. Cats are smart but we must remember they still have a limited capacity to "understand"...they just act out of pure instinct. If you yell at him, his basic instinct is to hide, if Pen isn't present anymore, his primary instinct will be to call her. Now that she is gone he'll keep calling her but he'll get used to his new life.
Take care hun, and God bless you for being so caring of your animals...and don't forget to send cute pictures of Luff and Sage.
These two...i look at them everyday and see more traits of Pen and Shanks...It feels like those two are trying to send messages through them letting me know their ok. Maybe i'm crazy because i havnt slept good. Hmm dunno but Sage and luff sleep with us everynight and dont like to leave us to much. Luff stays in the comp room with me and sage and he's been fathering her alot lately. He cleans her and snugs her and i've seen him escort her all around the house. He's...so charming :3