I had a conversation with a friend about this exact kind of thing awhile back. We realized we had opposite expectations. She was under the assumption that people just kept stuff she told them secret unless specifically told that they could share it. I operate under the opposite assumption: that nothing is a secret unless the person sharing it specifically says not to share it (that applies to myself as well).
Regardless of which assumption one operates on currently, it’s much safer to operate under the latter one (I highly recommend it).
Family can be even more complicated, because in my experience even if you tell a family member to keep something a secret, that usually means, to most people, “keep it a secret from strangers” and you can bet that your other family members will find out about whatever it is you told that person.
The “without being signed in” part of YouTube is now no longer completely true. I tried to watch a video tutorial at work the other day and it wouldn’t play because I wasn’t signed in and so “they couldn’t be sure I wasn’t a bot”. I’m not signing into any personal stuff on my work computer, or wasting time creating a “work” Google account, so I guess YT can no longer be a place where I can get helpful programming info.