IMHO, there will likely be some growth and independence in the next two years before he goes into middle school.  He still may not be the most emotionally advanced kid.. but he may do better than you think.. and may develope more independence naturally.

I also feel like you need to be careful to not equate size with maturity.. 9 may be a little on the young side to hold mom's hand.. but it's not totally out of bounds... and unless you see it as 'resource guarding' to prevent YOU from being close to your wife.. I don't think you will gain anything from this becoming a fight.

in the end.. it isn't a hill to die on... he will likely naturally become more independent.. and I don't think mom has to shake off his hand for that to happen.... other peers will likely be shaping this as he sees his peers not doing the same thing.. and it will become uncool to HIM.

You pushing to address this will come to no positive outcome.. I would keep this opinion to yourself.

Remember... he is 9 not 19... he is a kid.. they don't have to start thinking about their life outside their immediate family.. he isn't moving out next week.

I went back and read your other blogs and it seems that your SKs are on the Disneland Parent Coddling Fawning Holding Back from Development Program that we often see here. 

I feel for you. My SKs were on the program and like other SKs on the coddling babyfying program, they did not meet ANY milestones at a time that their peers did, if at all. Your DW is the one fostering this dynamic and making sure her kids are never able to leave her. This dynamic almost always results in the step-parent getting the short end of the stick and only crumbs for marital love and attention, if any at all.

Ask me how I know.

Also, you don't have a SK problem, you have a DW problem. There is something within her that is causing her to foster this dynamic and it's bloody hell to get your spouse to see it or even want to change it. You're the one who is unhappy. If your spouse is not unhappy, there is no incentive to change anything, so the spouse will do everything in their power to dig their heels in to maintain the status quo. In my case, my DH actually sabotaged any sign of growth in the SKs because he "just couldn't afford to lose the kids." It took more than one epic shit fit/come to Jesus meeting on my part and intensive, long-term therapy for both DH and I and couples counselling to get changes but that was because DH was finally willing to change when he became profoundly disappointed in how my SD34 turned out and when he realized I had started executing my exit plan. It's been a very very very tough road. 

Good luck.

Oh, and you're not crazy or wrong. You're living in an untenable, sickening situation. 

Last night we had to go to Publix for a school event.  It was math around Publix.  They had a work sheet and a fake budge of $100 where they had to come up a shopping list within their budge for an imaginary pizza party.  Mine definitely didn't want me lingering close by whatsoever and would have died of embarrassment if I tried to hold her hand in front of friends and teachers.  I definitely think she is doing him no favors by not fostering independence.

I wouldn't worry or focus too much on the handholding. That will not go anywhere good. It's the sort of thing time and peer pressure will take care of.

SS13's BM is somewhat guilty of coddling and babying. This kid still thought baby talk and playing baby were adorable three years ago -- at age 10. She and her parents were encouraging it.

Anyway, it's the sort of thing that's frustrating and annoying, but I'd keep quiet about it unless she asks you. Chances are, he'll drop her hand on his own soon enough. (Now, if he tries to drop it and she clings on for dear life, that's a different issue.)

If there's co-sleeping or nighttime disturbances or bedroom violations, that is absolutely in your lane and something you should talk to her about. But keep the focus on you and the impact on you -- not on her failings as a parent. That leads to defensiveness.

Luckily, my DH isn't the babying type. And he has a firm "no kids in bed" rule. Recently, SS started coming into our bedroom after he brushed his teeth right before his bedtime. I usually take out my contacts and put on my pajamas then and the dogs follow me -- he wants to pet the dogs, so in he walks. I said something to DH and he told SS our room is invitation only -- except in cases of real emergency.

Optics aside, my mom and I walk arm in arm regularly.  I'm 60, she is nearly 80.  We have always done this. As have my mom and my brother.  A 9yo holding hands with mom is not necessarily an issue.  

If the 9yo is blocking you from physical contact with your wife, that is an issue.

Growing up mom and my brother and I traveled often without dad. He would follow us later.  My parents where young when they married (17 & 19) and when they had me (19 & 21), I'm the eldest of 3.  When I was in my mid teens to mid 20s mom and I would often get snide looks and comments from the nosey people and the blue hairs who made assumptions regarding our relationship.  Mom and I would torture them for a while, then after spinning up the smirk faced blue hairs to a near state of appoplexy I would drop a "Mom, what do you want to do for lunch?".  We would then laugh our asses off while giving the nosey and the smirk faced blue hairs a "Say something now!" look.

He will make some huge advances in the next 3 years.  Though I would say having a talk with your SO about your observations and concern

s is warranted.

My SS's thing was to rush to open doors for his mom.  He would do this to the point of sqeezing between us or between me and the door that I was preparing to open for my DW.  Even now, he is 31, he is very proactive about openning doors for his mom, GMs, Aunts, etc....  While his overly engergetic execution on door openning when he was kid used to irritate the crap out of me, I would correct him, then thank him for treating his mom respectfully.  That modified his execution behavior.  

So, focus on discussion and correction.

IMHO of course.

Good luck.

My 10 year old 4th grader still holds my hand sometimes. Not in front of her peers, but if it's just us on a walk or if we're traveling, around the airport, or walking around a city. I really don't think it's that unusual. And as others have mentioned, it's something that will likely taper off naturally going into middle school. If there are other examples of clinginess or enmeshment, then that's a different story. But the handholding alone isn't cause for distress, in my opinion.

If y'all are on a date ... No - spouses hold hands. 
 

If he's one on one with his mom ... whatever floats their boat 

IMO

With the GK. Like crossing a big , busy, street, or in a big crowd. And getting rejected by them .  Time will tell