It is unlikely that they will, since they would have to be elders by now, but if they had kits, they could join. We don't know what happened to Ruby and Socks after The Rise of Scourge, but Erin Hunter confirmed they are alive, so it's possible.
Echosong joined SkyClan because she kept on having dreams about SkyClan's ancestors. Although Echosong is the medicine cat of SkyClan she has no SkyClan ancestry.
No, they were the first.
It is not stated.
Hattie is a kittypet, but she is mentioned in "Hawkwing's Journey" as the mother of Hawkwing, the SkyClan deputy. She had a brief relationship with Sharpclaw, a SkyClan warrior, but ultimately decided to stay with her twolegs rather than join SkyClan.
Yes, Firestar's unknown faith mated quince making scourge,socks and ruby firestar's half siblings
Jake. He was also the father of Scourge, Socks, and Ruby. Scourge, Socks, and Ruby are the half-siblings, because they shared same father but had different mothers.
Socks is his brother and Ruby is his sister. Firestar and Princess are his half siblings( they have the same dad. Jake.) Quincey Was Scourges mother
I doubt it.
Yes. Echosong is medicine cat of Skyclan.
Yes, and it is called Skyclan's Destiny.
its Starclan and maybe.
The ISBN of SkyClan's Destiny is 9780061699948.