Story where dru brings a 4year old Buffy home 2 spike and he knows that's his mate.

Idk if Buffy is really 4 but she's really young around that age. And spike leaves with Buffy and never goes back to dru. But watches over Buffy until she's of age. Been trying to find this story.

You are probably after this fic by Holly, and yeah, I think she is 4 when they meet...

In Omne Tempus by Holly
For a hundred years, William the Bloody has led a trail of bloodshed and chaos across Europe and the Americas. That all comes to an end when the woman he's devoted his existence to brings his mate to him in the guise of a late-night snack. A small girl with eyes of green and blonde hair. And suddenly, Spike is thrown into a world of color beyond the black and white, and his life is never the same.

Omgoodness thank you sooo much ScoobyDawn )) I think that is it.