There are pairs. Matching one Greek such as Theseus and to a Roman such as Romulus. There is also a double pairing of the Graachi Brothers to the Sparta Kings Agis and Cleomenes.

Ancient writers didn't really use chapters, what we call books is usually just how much would fit on a scroll. There are missing scrolls which is why you can't read all of the lives and some won't have their partner. If you're going to get into reading classical sources your going to have to deal with such sad facts as someone losing the Caligula Chapters of Tacitus's Annals of Imperial Rome.

I ask mostly to point out that there is much to be said for not reading the Lives in one sitting, and to lament that modern editors in their wizardry have seen fit to remove the versing or, as XenophonTheAthenian remarked, "book, chapter (or line)." I had first noticed the detailed versing of ancient texts from J.M. Cohen's abridged Montaigne and was angry that the copies I went out and got to read as Montaigne did didn't have the versing.

Plutarch I don't think intends for people to read a life in one sitting, one remark he makes, in the Life of Timoleon, speaks to people taking their time - here he's justifying what might be thought digressions - :

Such anecdotes will not, I conceive, be thought either foreign to my purpose of writing Lives, or unprofitable in themselves, by such readers as are not in too much haste, or busied and taken up with other concerns.

Plutarch has been called superficial, but there's often a lot to digest, take the first paragraph of the Life of Pyrrhus for example:

Of the Thesprotians and Molossians after the great inundation, the first king, according to some historians, was Phaethon, one of those who came into Epirus with Pelasgus. Others tell us that Deucalion and Pyrrha, having set up the worship of Jupiter at Dodona, settled there among the Molossians. In after time, Neoptolemus, Achilles's son, planting a colony, possessed these parts himself, and left a succession of kings, who, after him, were named Pyrrhidae; as he in his youth was called Pyrrhus, and of his legitimate children, one born of Lanassa, daughter of Cleodaeus, Hyllus's son, had also that name. From him, Achilles came to have divine honors in Epirus, under the name of Aspetus, in the language of the country. After these first kings, those of the following intervening times becoming barbarous, and insignificant both in their power and their lives, Tharrhypas is said to have been the first, who by introducing Greek manners and learning, and humane laws into his cities, left any fame of himself. Alcetas was the son of Tharrhypas, Arybas of Alcetas, and of Arybas and Troas his queen, Aeacides: he married Phthia, the daughter of Menon, the Thessalian, a man of note at the time off the Lamiac war, and of highest command in the confederate army next to Leosthenes. To Aeacides were born of Phthia, Deidamia and Troas daughters, and Pyrrhus a son.

Look at all those utterly foreign words! Now you can say that a Life can be read in one sitting, but if you are going to do anything other than gloss over unknowns, that is, if you are going to study at all, then it's gonna be impossible to do so in one sitting.

I especially like the guide that Plutarch is concerning ancient geography, stopping to check on a couple of maps that I've printed so that I can see the locations. And, obviously, to learn anything about the supporting dramatis personae, takes some wikipediaing.

When you resolve yourself to what is the last resort - counting the paragraphs as chapters themselves (this is the Clough Plutarch here that I'm talking about) it is a very cool experience. Trying to slog through forty pages of the Life of Alcibiades all at once is something that I can't really do without disgust.

I also like to experiment in this way: is it better to read the wikipedia before reading the Life, or the Life, then the wiki; Life, wiki, Life....does that bring you even close to knowing it all? Probably not.

Anyway there's a richness to Plutarch unparalled. Obviously that's the least controversial statement about an author ever, as millenium raise him to the cream of the crop, and yeah it's shit that they don't have the verses and I should probably go through and number the paragraphs even with a bit of a starving artist versing - guerrilla versing - .

All the best, here's a quotation to finish up:

[B]ut it is a general feeling of all who have occasion for wicked men's service, as people have for the poison of venomous beasts; they are glad of them while they are of use, and abhor their baseness when it is over.

Life of Romulus