I would tell your husband that unfortunately the host for the wedding stag is your son and it is up to him to decide who he wants to invite.

I would also advise your son to consider carefully the fallout from not inviting his step brother. It is likely to cause hard feelings. Maybe he could enlist someone to corral the SS if he starts to get out of hand?

And like Echo said. He needs to be upfront with his stepbrother why an invite isn't forthcoming.

I really feel for your son. This is a no-win situation for him. And I can't blame him for not wanting to invite narcissistic SS to his wedding. Would your DH be willing to speak to SS and let him know that the wedding is about your son and that he wants him to focus on your son, rather than himself? Or possibly make a deal with DH that he takes SS away from the wedding at the first sign of obnoxious behavior, and you will let him know when.

The problem with narcissists is that they can not be convinced that their behavior is unacceptable. I have some rather sick and vile ideas of how to take care of it - to cause him to have to leave the wedding early. Not very nice, but an option.

So is it just the stag party that he doesn't want to invite him to or the wedding too?

This is one of those damned if you do, damned if you don't decisions. Not having ss @ the stag party is easy if ss hasn't told him and DH all of his plans. The guys and ss can go out for beer and pizza for a few hours at lunch then all *go home* but really meet up at the real party later, just keep any photos off of social media. Crappy high school like move but effective and perhaps necessary in avoiding WWIII w/ss and DH. The wedding I would say yes, invite him but like ESMOD suggested have someone (not DH) corral and babysit him (like put a sleeping pill in his drink }:) ).

I don't really consider stag party being a "family event". It's for your son and his friends hosted by one of his friends or groom's wedding best man/groomsmen.

He's under no obligation to invite his stepbrother to it if the two don't particularly normally socialize. You did say "family event" though, so if that means every last male related to and connected to your son (your DH, uncles, cousins blah blah)I can understand your DH feeling the only person not invited and attending that is a male is his son. Awkward.

I'll assume, since you didn't mention the wedding nor the reception, it's just the stag party SS is being excluded from? If so, your Dh needs to understand that the stag is for your son and your son isn't wanting to share his party with someone who has attempted to turn the focus off of the honoree of the party. This one is all about your son. Spotlight on your son. Friends and wedding party males that your son is close to. Unfortunately due to your SS's narcissistic personality that does not include him.

The risk that the groom is taking here, sadly, is that the SS defines loyalty and social convention in the same thoughts. In other words, son must ask himself, what do I have to lose by inflicting narcissistic injury on this man?

The reverberations could last a long time, or SS might not give a hang about being invited. Only your family can judge that.

I had a situation where my son refused to invite my sister to his wedding. Now, that hurt me, but I went along with his wishes because the day was about the marrying couple. However, my sister's on,y crime was that she was a naggy old witch. Not poisonous ot disruptive. Son simply didn't enjoy her company. It did hurt her feelings, probably more than he knows.

I think your son needs to seriously think about what he fears, and stop simply thinking about what he wants. A step brother is a close relative whether he likes it or not, and the future price of "this is my party" reaction may cost him dearly in the future.

Yes, and the guy party is usually the more important invitation not to be missed, to most young men. The wedding he would probably be glad to skip.

Narcissism never goes away. I have a 51 yr old sister/golden child who ruined my DS and DIL's trip to go see my aging parents. DS and DIL were subjected to an 8 hour car ride of whining, complaining and TMI.

On top of that, sis whipped my parents up into a critiquing frenzy (not hard to do) and the atmosphere became poisonous. My parents are judgemental religious cultists who overlook my sister's infractions of practically all their rules, whilst holding everyone elses feet to the fire. They ended up driving back without her. She stayed and continued to mooch off of my parents.

No to the stag party unless you can roofie him up and wheelbarrow his carcass into the coat room where he won't remember anything until he comes to.

Insanity is doing the same things repeatedly while expecting a different result. Your son knows this and is not inviting his SB. Your DH ... he is insane since apparently he expects his toxic spawn to be well behaved at his SB's wedding.

IMHO of course.

Good luck.