Angel didn't directly sire Spike, Drusilla did.
The Master -> Darla
Darla -> Angel
Angel -> Drusilla
Drusilla -> Spike
One great Pairing also known as Angelus and spike (when angel goes bad) they bicker with each other pretend they hate each other but secretly they like each other, and not in the sexual way as many S/A fans think ... Angel sired spike along with Drusilla (long story) anyways they are connected and kind of related in that way so em basically there 2 hot sexy vamps with souls.
see Angel and Spike
Spike: You are soooo stupid angel honestly
Angel : this coming from captin peroxide?
Spike: Bloody ponce
Angel : we are trully hot
Spike : that we are .... that we are