I’m sorry you feel this way.  Please forgive me as this is my first post but what you said about how you feel about your step son makes me really sad.  My son, who is 10, is the kind of boy you described.  Really likable, polite, just all around a good kid.  His bio dad feels the same way about him as you do your step son.   Some kids are just sensitive.  My son is and his dad can’t stand it.  The worst part is, he has a twin sister who is the opposite.  Let me tell you he absolutely knows how differently he is treated by his dad than his sister is.  As my son gets older, this will cause him to separate from his father.  I know it’s different with you as you are the step parent but if you can’t treat this boy with the same love and respect you do for his sister then you should walk away.   It’s not fair to him, your wife or his sister.  I hope you can find a way to show him kindness and respect.  It sounds like he deserves it.  

this child is for all purposes kind hard working and respectful. You acknowledge this. So the problem here isn’t a badly behaved child or your SO not parenting as are the usual cases on this forum. 

You seem to only respect those who can show strength through physicality and seem completely uneducated on other types of strength that can exist. Even when this child commits to a martial art and excels at it, you still aren’t happy - he has toughen up but it’s not enough for you 

honestly with this frame of mind nothing that child does will ever be enough for you

you and you alone are bringing unnecessary unhappiness to yourself and many of those around you. Only you can change you. Only you can change your mindset. 

I suggest you try counseling as a starting point. If in 3-6 months you still feel the same way you must leave and not get married. Do not subject this child to your impossible standards and do not subject yourself and your family to that sort of tension and unhappiness

It’s pretty darn normal. I suspect my resentment of SD might be related to that primal thing you reference but at the same time SD is not a nice girl, she is jealous, self centered, rude, manipulative and inconsiderate. And she has no friends so it’s just not me.

So you're all Brady Bunch except for this one kid. Man, I'd hate to be that one kid.

Go back and read your post. The conflict in it is fascinating. "He's a great kid" -- "I can't stand him." Either he's a great kid or he isn't. It almost sounds as if you're...jealous? Nah...not jealous...maybe threatened by this kid? Maybe not that either. Regardless, you admit this is squarely on you and your issues.

Even if these were all your biological kids, you might find this one contrary to your nature. You seem to appreciate a manly man, but HE'S A KID, not a man. If he doesn't like tickling, don't tickle him, even if he seems up for it. He might be trying to be what you want him to be (like the other kids) and he just isn't. So don't go there with him. Meet him where you intersect: do jujitsu with him. If he likes to hike, hike with him. Find common ground with him.

You don't have to love the kid, but expecting him not to be "weak" at 11 is ridiculous. Surely you see all the kids are not exactly alike, even though you lumped the rest of them together. This is who this kid is a mere 11 years into his life -- he's practically still a baby. Who were you 11 years ago? Give him a break -- he has another 14 years to develop!

He's at an age when he is going to start rapidly transforming -- all your kids are. The ones you most like now might become the adults you least like. You don't know who they're going to become. But if you come down on this kid with all this disdain, you'll fulfill the very weakness you most dislike in him. That's kind of weak on your part.

Help him become a confident man. You're clearly a big boy who fancies himself strong and confident, but your post reads...kind of weak of character and will. If you're really strong and confident, you won't be beholden to your "primal" dislike of this kid. Use your strength to connect with this kid -- he might be the one who needs it the most. And he might end up being a cop or a CEO or a world leader someday. Don't divest because of who he is at 11.

In some parts of the animal kingdom - the males are seen for dust. In some parts of the animal kingdom, the whole group looks after the offspring. But we're not the same as other animals and we have a more complicated way of doing our relationships, which means even the dynamic of the adult male rejecting the offspring of another were true then we'd be able to overcome it. Frankly suggesting that is just as sick as suggesting that your stepdaughter is being groomed to be some kind of sister-wife. Hey, the lions do it - why not us?

1. So we know where you are at:

 You get points for honesty. You do not like the kid. Ok. This is where you are at.

2. What is your endgame:(once you know where you want to go you can plot a course)

What exactly are you trying to accomplish in regards to SS. Are you trying to like him? Are you trying to ignore him? Is just coexisting a possibility...?

A bit of story.

I love my SS12. I see much of his mother in him. It makes me dislike him when he acts like his mother entitled, annoyingly whiny and sniveling and lazy. I am very clear on the fact that i dislike the behaviors he exhibits. When he acts lile his mother I remind myself that he is compassionate, caring and rambunctious lile his father( my husband). 

So maybe when your SS exhibits the frustrating behaviors you describe you could see the qualities of his mother(your future wife) in him and work to hone those. 

I have thought similar things to what you describe about my stepson. I am a stepmom, not stepdad as you are, but it feels primal to me.

One thing is different. My stepson was horribly behaved when I met him, and for years after. If I am honest, I must say he has improved. I still find I do not like him, and it is exactly as you described. I hate his voice, and everything he says. My entire demeanor changes when he walks through my door. I cannot stand to look at him. Objectively, he looks more like my husband than his mother, but in all, he looks like "definitely not mine". He has a stupid name, a stupid haircut, and wears ugly clothes. "Definitely not mine", like I said.

I think for both of us, this is probably a biological reaction. As you said, in the wild, the males push the younger males out of the pride as they come of age. Of course, as humans, we cannot do this, as you said, but the instinct remains.

In my case, a biologist friend made the best comparison to me. She said, "It is as if someone dropped their baby in your nest and they expect you to feed it, even if it pushes your own babies to the side." Of course, this sort of behavior is in common to birds. I thought this was accurate, and maybe it is relevant to you as well. We are expected to commit many resources to our stepkids. You are expected to do this more than I am since your stepkids are there 100% of the time and mine is 50% of the time, but in both cases, we are expected to divert resources from our own offspring to this "Definitely Not Mine" offspring, and that goes against everything we want to do biologically. I do not know if you read any books on stepparenting, but some of them talk about this tendency in birds also. Of course, we are not birds, but at our most basic level, we are animals, so these tendencies exist no matter if we like it.

In some small way, it helps when I acknowledge this, if I say to myself, "Yes, I find him vile. He is not mine. I am programmed to want to throw him into the street. I am overriding that programming by feeding him. Just look at me feeding this strange looking baby that was dropped into my nest."

I also keep a bottle of vodka hidden just for me. This helps.

I am a step dad and I dealt with exactly what you are feeling early in my relationship with my incredible bride of nearly 24 years.

I refer to this as a mammalian response to the spawn of another male being in your home.  Kind of like when a new male lion takes over a pride and instinctively kills all of the young progeny of his predecessor in order to get the females to go into estrus.  Fortunately... we are humans and can make different choices. 

My SS-25 was 15mos old when his mom and I met. We married the week before he turned 2yo.  I had a visceral reaction to his presence in my home while we were dating.  Not all of the time but when I had those episodes they were extremely strong.  What I knew was that I wanted to spend my life with this incredible woman and for that to happen I had a choice. Either go all in and be my SS's father or have a tense likely limited duration 2nd marriage. 

I chose all in and started taking the actions of love. I held his hand, I put him on my shoulders, I played with him, we chased ducks around the golf course together,  I read to him, we went on "Johnny Quest"  adventures together, etc, etc, etc... In not too much time I started feeling love for him.  The actions built the feelings. My dad was very active with my brothers and I. He wrestled with us, we did guy stuff together.  That is what I knew and that is what I tried with my SS. He is not a physical guy and never has been.  Though we did do some wrestling and tickling he hated it for the most part.  So, I had to adjust how I engaged with him. And I did.

So nearly 24 years later and back at the ranch... my SS-25 and I are extremely close.  I am his dad.  I chose to be his dad. Sure, we had some struggles and on  rare occasion my male lion mammalian visceral aversion to his behavior would catch me off guard but I made a different choice and I remained his dad.  I too run a tight ship.  Fortunately his mom is a structure and standards focused parent as well. I/we firmly believe that being parents who set and enforced behavioral and performance standards is in large part why we are all so close as adults.  While we set and enforced standards we also came to realize that he had to be who he is and not who we thought he should be.  We accomplished both things together.   He has been in the USAF for 7+ years and will turn 26 in a bit more than a week.  He still isn't a physical guy though he works out like a fiend. I am proud of him, I am proud to be his dad, and I love him unconditionally. Even when he pulls a young man brain fart upon occasion.  I call him on it, we talk about it and I let him live his life.  He either considers my advice or he doesn't. Either way he lives with the outcomes of his choices.

He asked me to adopt him when he was 22. We made that happen.

So, while I completely understand  your visceral aversion to this kid... you have a choice to make.  Take direct and different action with this kid, be his dad and continue your life with your incredible bride... or.... move on.  I am confident that if you take the actions of loving and parenting him... you will love him ... and he will love you.  The actions grow the feelings.

It has worked well for us..... so far.

Good luck.