As you know, Spike's parents are likely dead. However, is it so impossible that he can't have an aunt, uncle, grandma, grandpa, older brother or sister, or something out there ALIVE somewhere?
Let's face it, Spike is the only one in the Gang of Seven that appears to have NO actual family from his own species (which would exclude Ducky and her family).
That has to be a bummer for poor Spike. I know the tone was a bit like this in VIII, but what if a member of Spike's family actually did come? (Maybe they could end up among Tippy's herd, come to the Great Valley at one point, find Spike, and realize that they have found a long lost relation. I know it's a long-shot, as Spike would have been an egg when they'd have last seen him, but perhaps the relative knew Spike's parents and would recognize Spike as being as such just because of the resemblance he bears to them, and, happening to hear of how Spike was found and where, realizes that Spike is a long-lost relation.)
Anyway, now I have another LBT fanfic idea.