I have two which have twins in them, though they show up later in the story/series, not right at the start:
Spirit Indestructible by Passion4Spike Rated: AO-AdultsOnly Summary: Season 5. Begins with 'Spiral' in the abandoned gas station, and goes *far* off-canon almost immediately.
When Dawn makes the ultimate sacrifice to save her sister, friends, and the world, Buffy's mind snaps. When Buffy's friends give up hope of her ever recovering, and become afraid that she'll turn violent and uncontrollable, they call in the Council to help. Fearing what the Council will do, Spike, forgotten and ignored by her friends, steps in. Will he be able to reach the Slayer when no one else could? Will he be able to keep her out of the hands of the Council and away from her 'helpful' friends? How much heartbreak, guilt, and failure can one girl stand before her indestructible spirit finally resigns the fight and gives up hope?
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Unexpected Universe Series by Passion4Spike Summary: This series of stories picks up at the end of Season 2, The Becoming 2 and goes off canon about half way through that show. You'll find familiar challenges for Buffy and the Scoobies with UNEXPECTED results as Spike faces them with her. If you like a story with love, romance, sex, fights, angst, tears, laughter, marriage and babies then you're in the right place! I hope you enjoy it!