How repulsive.  I gather SS is 13 - I would have expected him to start paying attention to personal hygiene by now, frankly.  But then a lot of SKIDs that we hear about on this site seem pretty stunted when it comes to developmental things like this.  My own SDs used to secrete used sanitary towels in their bedroom drawers for me to find weeks later, at around this age.  Not sure why, as we had a special bin in the bathroom which they knew about. 

It's pretty common for 12-13 year old kids to not care about hygiene.  My SS was like this at 12, except that DH wouldn't let him get away with it.

What's up with your DH that he doesn't monitor this stuff and order him to change his clothes?

Not a SS problem.  If your DH would parent his son. There would be no problem.  

Children of Divorce often end up stunted in various ways because they get parented differently after their parents split up. 

Sometimes it's guilt, or a fear that they'll lose their children if they correct them, or the tendency for a NCP to treat their kid as a visiting guest, but the skid is allowed to run feral. Neither parent takes responsibility for being the bad cop and teaching their kid(s) basic standards of life skills, so CODs end up with deficits. Show me a kid who's dirty or not properly socialized and I immediately wonder if they're 1) from a dysfunctional home, or 2) a skid. Often it's both.

You SO needs to sit down with his son and explain that daily bathing is mandatory, good hygiene is important, and taking care of his body so he won't be the STINKY KID at school is non negotiable. If you couch it as being concerned and wanting good things for SS, maybe your SO will step up.

I'd spray his ass with fabreze anytime he entered my breathable air. Shame on your DH for allowing this to continue.

Normal kids bathe because their parents make them. Mine did not start to do it without being made until they became of age to want to date. So, around 12-15. The problem with some skids is nobody wants to take control and do the work of parenting. Reasons include fear the kids will like the other parent better, and laziness/incompetence. 

All skids here shower before school everyday. (SS17, SS15, SD13) SS17 never brushed his teeth. Only brushed them when he had his gf. SO use to make them brush before bed every night too when they were little younger.
 

NOW summer and covid... different story. SS15 has always had good hygiene showers, changes clothes, brushes teeth. SS17 is only showering now because of work. SD13 does not have good hygiene. She will go days without showering, not changing her clothes. (Usually up to 3 though) She surprisingly doesn't have her period yet but, I'm sure it's coming very soon. (she's 5'9" around 170lbs) I think once that happens things will change with her. I've tried really hard with SD for to get better hygiene but, only so much I can do. 

I don't remember my brothers (2 and 5 1/2 years younger) going through that phase. We all always had great hygiene. 
 

Well I and my sister were required to bathe every night if we had been out playing and every other day otherwise probably ages 6-12? Until puberty then every day. Always put on all clean clothes. Brush teeth 2x per day...you know, the basics.

oSD was like your SS up until she left our home at about age 13.5. she has begun to shower more like every other day but she wore filthy clothing and stank horribly by the end of the weekend often. Once I literally gagged when she walked by. No teeth brushing either. Parents did not do anything ever...my discussing it with DH never resulted in change so I gave up.

YSD is better but I just told DH the other day she needs to start showering more than once every three days and brush her teeth in the morning AND wear her deodorant. Because she stank. DH said, "She's showering more than she used to." Me, "Still not enough, you were not as close to her as I was, and you don't believe me?" DH, "I didn't smell her." Me.....done with convo forever more and will not be close to her again. Funny thing is DH has experienced this before and complained but nothing changes. Because parenting firmly is beyond him, corrections are impossible even if they are needed.

So what age do kids normally know to put clean clothes on after a shower? To just take a shower without being forced? Brush teeth every day?

By age 2 DD is putting her own dirty clothes into the front loader. And insists on showering after a mess - sometimes too many times a day. Brushes after every meal. But it's really just the parenting. She didn't magically figure out where dirty clothes go one day. She's been trained early so by the time she's 11 it'll just be a fact of life for as long as she can remember. Be responsible for your own messes. So the answer to which age do they start to care? Whatever age their parent makes them care. 

This is exactly why stanky kids need the hairy eyeball of parental supervision.  They bathe daily as told. Their dirty clothing is taken and they wear clean clothes.

Hygiene is mandatory and if they fail to catch a clue and make it happen on their own, they are treated as toddlers and it happens to them rather than them doing it for themselves.

We used to have to deal with the occasional nasty New Cadet at Military School.  Upon occasion parents ran out of patience with difficult kids and dumped them at Military School. Those kids did not stay stanky for long.  The were told ... .once... to bathe and put on clean underclothes and uniforms.  Once. If they failed or if they attempted to stand their ground they were introduced to midnight shower parties by their peers.  I do not recall a single incidence when a second midnight shower party was necessary.

We had to do a tune up with SS when he was 17.  He swore he was showering and washing his hair.  I believed him. He would go in his bathroom, shower, come out obviously bathed.  Then a few hours later after he dried off his hair was insanely greasy and his head stank like a dirty wet dog.

So, I finally told him  to put on his swim suit and hit the shower and that I was going to watch him shower.  He was not happy about that but I made it clear that it was obvious that something was amiss.  He jumped in the shower, grabbed his shampoo bottle, turned it upside down over his head, then squeezed and proceeded to scrub his hair.  The problem... the bottle was empty and had been for months.  He then grabbed his bottle of body wash, squeezed it into his hand, lather up and washed  his body face to toes.  When he finished I busted out laughing. He was all "WHAT DAD! I told you I know how to shower!".

I then asked him to grab his shampoo bottle, take the flip cap off, and look in the neck.  He got an odd look on his face and started laughing.   That is when he learned why I had always told him to put the shampoo in  his hands before scrubbing his head.  After that, he made sure to put shampoo on the shopping list.  He also switched to bar soap.  It is a lot easier to manage visually than a bottle.

My Skid never had a serious stank and poor hygiene problem but teen boy brain farts certainly did apply upon occasion..