Hmm I could be completely misunderstanding your issue but I believe you might have the wrong structure in your content.
What I’d do is have a root for each site, set culture and hostname for each one (if they have different domains)
- Root A (root node for Site A)
- Blog
- otherPage
- Root B (root node for Site B)
- Blog
- otherPage
If, by any reason, you don’t want Root A to be present in the url, I would set, in appSettings.json, Umbraco:CMS:Global:HideTopLevelNodeFromPath to true.