Ferncloud and Ashfur share the same father, whose name is Whitestorm. Whitestorm was a respected warrior in ThunderClan and had many offspring, including Ferncloud and Ashfur.
his mother was brindleface. she was killed when he was an apprentice by tigerstar.
No, Ashfur does not know that Sandstorm is his half-sister. Their parent, Brindleface, is Ashfur's mother and Sandstorm's stepmother, so they are related through their mother. Their connection is not explicitly addressed in the series.
Ashfur's mentor was Dustpelt.
Now he does, since he's in StarClan.
Ashfur's mother is a she-cat named Brindleface, killed by Tigerstar in A Dangerous Path.
Ashfur-Revenge
Ashfur's murderer is Hollyleaf. Leafpool found a tuft of Hollyleaf's fur snagged in Ashfur's claws.
Lionblaze's mentor was Ashfur.
Ashfur misses Scourge so much, but Scourge and Ashfur could never be because Scourge won't go to cat hell, but Ashfur goes to Starclan anyways so Ashfur and Scourge will miss each other for eternity.
Yes, Squirrelflight is related to Ashfur through blood ties, as she is the daughter of Firestar and Sandstorm, while Ashfur is the son of Brindleface. In this familial relationship, Squirrelflight would be Ashfur's cousin, not his niece.
i don't think she should go into the dark forest. she didn't kill ashfur for joy, she killed ashfur shortly after a confrontation with their mother, squirrelflight, who turns out to be not their mother but their aunt, as it was leafpool and crowfeather who are the actual parents of hollyleaf, lionblaze, and jayfeather. Hollyleaf already knew about the true story about who their parents are, but during the confrontattion with ashfur squirrelflight revealed the secret to ashfur and so hollyleaf killed him so that the secret would not get out, but eventually she becomes so torn apart by guilt that at the next gathering she explains the whole thing. she didn't kill ashfur to save firestar, anyway and she doesn't belong in the dark forest because in the last book of the power of three she dies because of a cavein.