Buffy the Vampire Slayer Season Ten #14 confirms that Angel and Spike are literally the same person through blood. They are both connected to the same great-great-grandsire, Archaeus, whose shared ...

Angel was faced with an all-too-similar predicament to Spike's years beforehand in Buffy the Vampire Slayer's second season, when he first becomes Angelus.

Some think Angel and Spike should at least be referenced in the Buffy the Vampire Slayer reboot, and it would definitely seem odd if Buffy never talked about them.

James Marsters, who played the vampire Spike in the original Buffy the Vampire Slayer, addresses the series revival at Hulu.