Spike has a kid and it is not buffys. Can be either human fics or not thanks

The Special Two by Enchantress

Summary: Six years after the Hellmouth was closed, Dawn and Buffy are living happily in New York. One night Dawn finds out Spike is alive, and has made a LOT of changes to his life. So, what happens when Buffy and Spike realize they're living together in the same city, they're both human, and they're both parents?

You can find this one on Sinister Attraction. It says it's unfinished but it seems to be or at least the author left it in a good place.

Babies Daddy by Kimber

Summary: Spike Bledsoe finds himself between the rock and the hard place. To save his son he must choose between the love of his life and the child he needs to protect. Will his plans succeed, or fall to dust.

You can find this one here on SR

The Special Two is finished - it is misidentified on SR as unfinished. It's also my very favorite Spike as a father story. His relationship with his son is the best thing ever.

There is Baby Blue by Anaross

Spike/Buffy, Spike-Angel. PG-13. Set one year after Not Fade Away. Buffy finally comes to Spike. Can we spell "bad timing?"

Touch the Fire by William's Girl

Summary: Firefighter Spike Giles finds himself with yet another battle to fight as wildfires sweep through San Diego County. Out of the ashes of sorrow and destruction that he has come to accept as his life he finds hope, he finds love, he finds her...and it changes him forever.

I also found this old thread: Spike has a children Buffy is not the mother

Lies by Pet

http://dark-solace.org/elysian/viewstory.php?sid=2416&warning=NC-17

Summary: Despite the fact that she has never been in a serious relationship, Buffy Summers has already given up on love. One day she runs into a young boy and, horrified by his story, decides to help him. But, as she is about to find out, things aren't always the way they seem.

This Sweet Child by SunnyD. Post S.6 Spike returns human and Buffy rejects him. He leaves and later marries and has a daughter, The Initiative comes looking for him and his daughter, in the process his wife is killed. The only place he can think of to go for help is back to Sunnydale. Here's a link http://www.sinister-attraction.net/stories/s/sweetchild.htm