[33M] wants to invite the family of his child's mother to his wedding, but his [33F] fiancée is against it. Is this a reasonable request?

I have a 5-year-old daughter with my ex, and I'm really close to my ex's brother-in-law, who remains a good friend of mine to this day. However, there's an issue: my fiancée doesn’t get along with my ex’s sister. We’re a blended family—she brings three kids to the relationship, and I have one. My friend can be a bit blunt at times, which doesn’t sit well with everyone, but I know his intentions are good. While my fiancée is okay with him attending the wedding, she does not want my ex's sister there at all. I understand that if I invite my friend without his sister, he will likely decline. My fiancée thinks it's reasonable to exclude my ex's family from our wedding, while I feel differently. She’s concerned that the sister will update my ex on the wedding details, but I would have no issue if she did. I'm trying to present both sides fairly in this post because I'm looking for honest opinions on the matter.