We're seeing many questions about this! YouTube & YouTube Gaming subscriptions are merging, so videos from channels you're subbed to in Gaming will now show in your main subs feed: https://goo.gl/zfgfC4 If you think you’re seeing something else, please send a feedback report!https://twitter.com/FNecroShade/status/976850532626321411 …
We recently combined YouTube and YouTube Gaming subscriptions, read more about the update here: https://goo.gl/zfgfC4 . This might be related to your issue, but let us know if you don't think you've used YouTube Gaming.