Is 18yo still in high school? 

Kinda sounds like your husband is jealous and trying to make the lid miserable so he'll leave as after he graduates high school. 

Your husband picking on the kid and barking orders...sounds jerky.

He could be jealous, especially if he never had a close relationship with his own kids. Or, he could just be jealous of the time and attention that he feels takes away from him. Neither is a good reason to bark at your son.

How do you treat your son?

does he have rules? Does he call the shots? Does he make the weekend plans? Choose what’s for dinner? Does the household revolve around him? Does he clean up after himself?

is there a dad? What is his role? What is your relationship with dad?

i don't see enough info to pass judgement. By "very close relationship", what do you mean? How much time do you spend with your son, and does it encroach on your husband's personal space? From reading this site, i've learned that it is most helpful to focus on specific behaviors. Are there certain behaviors of your son that trigger your husband? Are there certain instances of your husband's behavior you find inappropriate?  

I have no idea if he is jealous - I don't know many adults that want to be 18 years old again and living with their parents, not much to be jelous of in my opinion. 

His attitude is not very friendly though, maybe you should try the radical appoach of  .....talking to your husband about it? Perhaps he can tell you what is going on better than we can with practically no information? 

Be warned though, your husband is not you and may not see your son the same way that you see him. You may also find that for change to happen in your home that your husband will not the be only one who needs to change - you and possibly your son will most probably also need to change too.

Or perhaps your husband is a just a jerk.

Also...how do you get a new husband when you have been married 7 years? I'm pretty happy with mine after 6.5 years but I think there are a few around here who might be interested if there is a 7 year option to trade-in the old one for a new model 

No one plans out or envisions their "happily ever after" with a child from the partner's previous relationship. That's really what it boils down to. Because you carried that child in your womb, watched him grow, and nurtured him, you are naturally going to view him with a preciousness and love that your husband genuinely does not have. And depending on how much your child is in your husband's household/constantly in his face, he may start to feel like an obstacle. Having to deal with another person's child can be extremely aggravating especially if the kid is old enough to be independent and out of the picture 

A couple of questions to honestly ask yourself:

1.) What kind of relationship have you allowed to foster between them? Did you not enforce household rules with your son, so your DH felt the need to step in and discipline? Or did you make him "bad cop" so you could be "good cop", and he's taking his resentment toward you out on your son?

2.) Is your son not as sun shine and rainbows as you paint him to be? A solid 70% of new posters here come in talking about how their spouse is an "amazing parent and partner", then spill out how that's not at all the case. My SSs are genuinely good kids, but that doesn't mean that they don't do stupid things that I find far more annoying than my DH does because they aren't my kids. And, if it weren't for my DH giving them twice as much hell if they disrespect me than if they did him, I'm sure they wouldn't show me the amount of respect that they do (because they didn't with their former SF, though I don't think that was unreasonable). If you say he's a good kid but he doesn't do his chores, doesn't have a job or extracurriculars, breaks curfew, snaps at/fights with you, doesn't show you respect or listen to you, or anything else, your DH is going to get really annoyed with him and not let it go as readily as you will.  ESPECIALLY if your son directs any disrespect towards you.

3.) Was your husband like this before you got married? Surely you had allowed your son and husband to interact before you wed so that you knew what kind of person you were moving your son in with. Plus, he has older kids, so I assume you saw how he parented. Is he different with your son than he was his own kids, and now you feel duped?

4.) Is it bad enough that your son is actually hurt by it, and if so, why do you stay in a situation where your son is being bullied? Either your son is the problem, in which case you need to put your foot up his backside (figuratively) and get him to straighten up OR your DH is a bully and you need to kick him to the curb for being an a-hole to your kid.

I agree with BethAnne above that you need to talk to your husband calmly and actually listen to his reasons for why he is behaving this way. Don't go in and ask, then tell him that he's wrong. His perception of your household may vary wildly from yours because he's not your son's parent. He doesn't have the same biological need to care for him and put up with him that you do. I'm assuming that when your DH's kids were younger that you felt similarly about his kids - that they didn't act like you thought they should, their dad or BM taught them things you didn't agree with, etc. Difference was that you got a break and didn't live with it everyday. Your DH does, though, and that means you and your son have to compromise on how you live just as much as your DH does.

Remember, you're a team with your husband, and your son benefits by you two working together and setting the rules of the home. You can't allow your son to have equal say, or really any say. He can share an opinion, but he's still a dependent in your household and doesn't have the same rights or responsibilities that you and DH do.

If after talking to DH you find that he's still actually being a bully to your kid, you seriously need to ask yourself why you put up with it and allow it to happen to your son. It's not fair that your son has had to live with a man who bullied, and continues to bully, him just so that you have a partner. If your DH really, truly is the issue, then it's a failing on your part for keeping him around. You don't get to bash how your DH treats your son but then not do anything to protect your son.

If this has been going on for 7 years, surely you have SOME clue what your husband's beef with your son is? Are you being honest with yourself that he's such a great kid? Are you enmeshed with your son to the point where you and he have an equal relationship to the one with your husband (ie, is he a mini-husband?).

My suggestion would be to LISTEN to what your husband has to say and try to figure it out - I'm sure he's given you some clues. Don't disregard them because you think your son is a perfect kid.

Your son has had to tolerate 7 YEARS of this???  
My husband picks at everything he does and never talks to him unless he is "barking orders".

I feel sorry for you son having to live like that since he was 11 years old. I hope your son is able to escape your H soon.

Need more information. I highly doubt it's "jealousy." That's a loaded term in stepland. Bioparents like to throw it around to shut down legitimate complaints about their kid. And because stepkids often do display jealous behaviors when it comes to a stepparent, these silly bioparents think that must be the same problem the stepparent has and that's why they don't "get along." Why? Because these bioparents somehow believe their children are equal to their spouse. And they end up treating their spouse like a child and the child like the spouse/adult.

Just because you have a "good kid" doesn't mean your DH thinks he farts rainbows like you do. And just because your husband doesn't get along with him right now, doesnt mean he is "jealous" of your son. Even really good 18 year old dudes can be annoying AF.

Imagine your husband had one of his buddies come stay. Or a niece or nephew. Usually it's fine for a short while, but after awhile you're really tired of the guest being there in your space. Overstaying your welcome is a phrase for a reason. Now imagine the husband loves having the buddy living there and cant relate to how you feel about wanting him gone and claims your just jealous of him giving attention to the friend.

Having a skid is very similar. Unless he was able to form a deep bond with your kid, it doesnt really matter if hes a great kid. Its probably annoyance/resentment more than jealousy.