There is a bit of backstory here. It's long. If you don't feel like reading it, that's fine, I understand.
So, when it came to inviting my mom's side of the family, she gave me a list of everyone including addresses, so I formed the invitations based on that. I messed up and overlooked sending a separate invitation to one of my 18+ relatives (say, Jane) who lives with her parents. As it turns out, she has a long term boyfriend who my mom did not include on her list either and I missed inviting him. Yes, my own fault, my own accidental rudeness. My mom called me to tell me that that particular family would indeed be coming to the wedding. I asked if she knew if it had been mentioned whether any of the girls would be bringing a date, and she said that they were going as a family, without any dates.
A few days later, Jane messaged me asking if her boyfriend was welcome to come. I apologized for my rudeness in not making it clear on the invitations, and said that I had no problem with him coming. She told me that my mom had said to her mom that it was just a close friends and family thing and that her boyfriend wasn't invited. I hadn't said anything like that to my mom, so it seemed like there might have been some kind of miscommunication. Since there seemed to be some confusion about it, I texted my mom saying that I had told my relative that she could bring her boyfriend. My mom responds saying that Jane's mom didn't want the boyfriend to come, because of some issue with the sleeping arrangements.
So what, Jane's mom has some issue with the boyfriend coming, but told Jane he couldn't come because I didn't want him there? Jane is an adult even though she lives with her parents, and has been with this boyfriend for about three years. They've vacationed together for a few months at a time, I'm not sure why the sleeping arrangements are an issue now when they weren't an issue then. They both would be paying their own way to get to the wedding (they are OOT guests) and paying for their own accommodations. Personally, I don't really think Jane needs to ask her mom's permission for her boyfriend to come to my wedding.
Anyway, I told my mom I wouldn't let myself be used as the excuse to not allow this guy to come, since I had no problem with him coming, personally. I tend to err on the side of communicating too much rather than hiding too much from people, so I just straight up told Jane that while I had no issue with her boyfriend coming, my mom was indicating that Jane's mom might have some issue, and while that personally I didn't think she needed her mom's permission to bring her boyfriend, I was just going to let them work it out amongst themselves.
This situation has pretty much been dealt with from my end and I am not getting further involved, but I am curious about what you guys would have done when confronted with the same situation.