Hi,
You've posted your topic in "Cortana" community,
You can click/tap on Community Hub (shown at the top of every page) -> Browse All Community Hubs to view the full list of all product related Hubs.
Xbox forum:
https://answers.microsoft.com/en-us/xbox/forumto answer your question, there is nothing strange. you and your friend must have added each others' Microsoft accounts to a family group or signed into each others' app.