I have done some testing - trying to share links to my brother. I have updated to iPadOS 13.5 but the issue is still there. I tried to share a link to this thread with him and it comes up with the Portuguese number.
If I copy the URL and paste it into Messages, it goes correctly. So I guess this points towards the share sheet.
if I try sharing the link to him from my iPhone, it works correctly - so it’s possibly an iPadOS issue but maybe not iOS issue.
I also tried sharing the ‘problem’ links to my wife’s iPad and it worked fine.
I will completely delete my brother’s contact details from my devices, re-enter them and test again.
If that doesn’t work, I’ll phone Apple support and see what they say.