I'm starting a new thread for this as I wanted to be able to discuss it freely. I have added a spoiler warning even though I don't actually know anything. In fact I barely know anything at all about this new series, I couldn't even tell you the name of the next episode!

Anyway, the Doctor mentioned having once had a brother. Could his brother still be alive? Could his 'brother' have a rather sinister chuckle?

How exciting!

Possibly