Order of the Phoenix

Not as far as we know.

No middle names have ever been revealed for either Aberforth or Ariana (although who knows, if someone asks JK Rowling on Twitter, she might make some up for you).

According to his Pottermore fact file - though I'm not sure if this particular part of Pottermore is counted as canon - Aberforth's full name is Aberforth Dumbledore, so he has no middle names. I'm not aware of any information at any level of canonicity on Ariana's middle name(s) or lack thereof.

As for why Albus had so many names: again, there's no canon statement to address this, but I can think of a few possible explanations.

• He was the oldest. When he was born, his parents might have been over the moon and given him lots of names, not knowing whether they'd ever have another baby to name. By the time his brother and sister were born, maybe they'd decided that such long-winded names were a bit silly. Note that "Percival" is named after his father, a common practice among parents at the time.
• He gave himself all those middle names. It's possible in Muggle society to give yourself a middle name that you didn't have as a child, so why not in wizard society too? It would fit Albus's character - "Nitwit! Blubber! Oddment! Tweak!" - to tack a few extra names onto his own, and it also fits with the relative grandeur of his career. Aberforth, content to remain in the shadows of the Hog's Head, doesn't seem like the type to bother giving himself extra names; and of course Ariana didn't survive into adulthood.

You have asked for quotes from the book which have never actually addressed it, but in the film Fantastic Beasts: The Crimes of Grindelwald (written by J.K Rowling) it's confirmed that Credence Barebone is actually Aurelius Dumbledore.

In around 1901, Aberforth had a son, Aurelius Dumbledore with a girl that he fell in love with in Godric's Hollow. However, the girl was "sent away," presumably by her parents, either before or after Credence's birth, although Albus was aware of rumours that there was a child. Due to the strained relationship between the Dumbledore brothers, Aberforth neither confided in nor sought Albus' help. Aurelius was eventually sent away to America with an aunt, where he was adopted by Mary Lou Barebone and given a new name, Credence Barebone.

In 1932, Credence attacked Albus and accused him of abandoning him, revealing to Albus that he was supposedly a member of the Dumbledore family. During a duel between the two, Credence's phoenix spread ashes on his body and Albus realised that Credence really was a Dumbledore and that he was actually Aberforth's long-lost son. However, by this point, Credence was dying due to his nature as an Obscurial slowly poisoning him, something that Albus sadly recognised from his experiences with Ariana. After foiling Grindelwald's plans at the walk of the Qilin, Credence, in poor health, accepted his father's offer to come home with him.

^{Dumbledore Family Tree}

So no, Albus and Aberforth were not the last Dumbledores. There was at least one other.