I would go. I'd also tell hubby to tell the nosy in laws to mind thier business. 

You should go. Make it known that you are part of the family.

When it comes to things like this, I am a great believer in doing what feels best for YOU.  Not for DH, not for the parents in law, nor the BM.  It sounds like you would like to go to this event - in which case, go and don't be infuenced by their stupidity. 

Personally, I'm always 100% thrilled when something happens that makes it so I CAN'T go to school productions. Recorder recital? Sorry - I have a meeting. 

However, your in-laws don't have any clue about this situation - so you do what feels right - which is probably going to the play. 

Is there a bigger truth here? Does DH need to spend more one on one time with this kid?

But for a school play - you're not actually spending 'quality' time with the kid -you're there to show support - and if you've been there for him - your absence will be more hurtful than helpful. 

From my experience, the more people turn out to watch a child perform the happier that child will be.

FWIW, my fear would be that if you don't go the child will think you didn't go by choice. And you don't want that, especially as you do seem to want to go.

Just a hunch , but it appears to me that BM may have played this deliberately.

She contacted the paternal grandparents, who of course were thrilled to be invited and receive tickets. She did it with a 'oh, tell Jr's father, there is a ticket for him too'. 

So the kid got three tickets for his paternal side of the family. Reasonable. One for Dad, one of SM and one for the little sibling. Cool. Sounds about per usual. However by getting the in-laws all excited , while Dad is clueless, BM managed to successfully rid herself of the 'undesirables' (aka, you and the other child). 

BM , IMO, knew exactly how to manipulate this event into exactly wat she wanted. Oh, no, she doesn't really want the paternal grandparents there either, but in her mind, better them than you. 

Whether you go or not is up to you. Yes, if you take the tickets away from the already and initially invited first grandparents, I'm sure the grandparents will whine and be hurt. Might even think you are selfish as you always go, do and be with skid and they don't. BM fixed you but good. You, not only got a high conflict BM, you got a sneaky b*tch in your BM.

Don't let this BM pul this off again, It is your Dh's responsibility to keep on top of his son's school and school happens. He should have direct communication with school and teachers. He should be elf informed of upcoming events and activities, the ins and outs of tickets/obtaining tickets blah blah blah. Not all, but most schools are use to dealing with divorced and/or two household children and the two sets of parents. Your Dh should not have to be being informed of production tickets by BM., BM should not be the one assigned to request and then hand out tickets. 

You have every right as an active Sm to participate. BM doesn't get a say. In the future, adjust accordingly and take her power trip away from her. 

*edited to correct silly typo

I can understand that the attitude of BM's family will have spoilt any possible enjoyment you might have had in the event, but I do feel that it's a damn shame that you should be prevented from something you'd like to go to, because of them.  Personally, if it were me, I'd kick up a huge stink.  

Your DH needs to call the school and see if it is possible for him to get enough tickets so that you can both go (and your kids if that's what you want).  You may find that they have restricted the attendance because I guess things can spider out quite a bit if everyone invites their spouses.. new spouses.. kids, grandparents, cousins etc..    If you do find that is the case then I can see wanting to give priority for the tickets to the people with a biological connection to the child.  But if there are no big limits on the tickets.. I see no reason why you should not go, if you want to  (me.. I would rather stab out my eyes than go to a kid performance... any kid).  YOu and your DH don't have to sit with the EX.. or the inlaws.  You can each visit with the child at different moments.  Shoot, novel concept here, you can all be civil to each other..lol.

I think you should be welcome wherever you want to be that your husband is invited.

Never have my SSs had a school performance that had a ticket limit - even performances at Christmas when the whole fracking school is doing something together. The only time I have ever heard of ticket rationing is with graduation or graduation-related events. Even then, most schools keep back tickets specifically for parents and steps.

I call BS on BM's reasoning. The only way she'll stop (or come up with a better game; this one is lame and easy to beat) is by calling her on her bluff. Call the school, ask about ticket rationing, and then ask for 3 more tickets (or 2 if your little one is small enough to sit in your lap) if there is actually ticket rationing. Then go with the tickets you get.

If BM loses her mind at the school, she is just going to make herself look bad. If your in-laws start clutching their pearls, remind them that YOU are the BM of their other grandchild, and upsetting you is a great way for them to see NONE of their grands (say it nicely, of course).

Yes, you are a stepmom. But You are also the wife. You are also a mother, and the mother of SS's sibling. All of those things combined MAKE YOU A FORCE TO BE RECKONED WITH. You are, and have been, an active part of SS's life. You are bound to your DH, legally and emotionally. Take a stand for yourself and your family, if that is what you want. If BM doesn't like it, then she should have considered those ramifications before she had SS. A little late for her to have a pity party now.

I actually think the best solution for this would be for your DH to say HE has to work and can’t go after all.... and then either you go with the in laws, or better yet send YOUR child with grandma and grandpa to see the play.

This right here will be what bites BM In her ass and makes it so she never messes with you guys again. 

There will be plenty of plays for your DH to go to, so really not a big deal. There is still a “biological connection” there by having your child with grandma and grandpa. 

It can be a pain in the butt for grandparents, and BM doesn’t get what she is after. I would totally manipulate it right back on her.

 Your DH needs to stand up for you. He doesn't deserve to have you if he cant.

He needs to draw a boundary with his parents that you are his wife and that you and he are a unit; that he won't tolerate games or you being  excluded; and that you do so much for SS and have a relationship with him. 

He needs to prioritize and protect you and the family unit you've created from all comers, including BM and his meddling parents. And he's needs to stop playing dumb and attempting to gaslight you.

I didn't read all the replies. My first question is, why is BM the only one with info about the school thing in the first place? Shouldn't DH have access to all things school related for his son, regardless of who is custodial parent? If it's left up to BM to relay info about these things then she gets to control the whole narrative. 

My second issue is the whole grandparents thing. They need to butt out and your DH needs to be the one to tell them not to involve themselves or let themselves be brought into things like this. A quick "hey, ds has a thing. Let me know if you can come or not" message would be appropriate IF BM is the only one with the info (which she shouldn't be anyway). The grandparents acting as go between for DH & BM is a recipe for disaster from the word go. 

If tickets aren't an issue (which could actually just be something bm is saying to exclude you) and your family wants to go with DH, then that's up to YOU GUYS. Not BM. I can't imagine my dh ever asking permission or even running it by BM whether he should bring his wife and kids to his own son's thing. Again though, this is where dh should already have this info on his own and grandparents shouldn't be involved. If you want to go or dh wants you to go, then call the school and find out about this ticket business and if possible, go! Nobody cares what BM thinks about you being there. At least you shouldn't.