They're products of the Bolotnaya protests.
Both emerged as political figures during the mass demonstrations that engulfed Moscow in the winter of 2011-12. Both came to Russia's opposition movement as outsiders. And both have built large and loyal followings on social media.
The socialite former reality television star and the tough-talking anticorruption blogger could hardly be more different.
But the political relationship between Ksenia Sobchak and Aleksei Navalny has now become ground zero of Russia's opposition.
It's easy to be cynical about Sobchak's announcement this week that she will run for president next year.
The dominant conventional wisdom is that she cut a deal with the Kremlin and agreed to be the token liberal candidate in exchange for being allowed back on state-controlled television channels.
Sobchak's candidacy will apparently help legitimize Vladimir Putin's inevitable coronation by generating excitement and boosting turnout in what everybody understands is a Potemkin, stage-managed election.
It also appears designed to neutralize Navalny, who will not be allowed on the ballot but who nonetheless threatened to be a disruptive factor from the sidelines by campaigning anyway and mocking yet another "fake election" between Putin and obedient, housebroken opponents like communist Gennady Zyuganov and nationalist Vladimir Zhirinovsky.
Sobchak herself admitted to meeting with Putin recently, ostensibly to seek his help in producing a documentary devoted to her late father -- and Putin's former boss and political godfather -- Anatoly Sobchak, who would have turned 80 this year.
But while using Sobchak as a patsy to legitimize and bring excitement to a dull, choreographed election and as a foil to blunt the Navalny factor may be the Kremlin's plan, there are also reasons to believe that this could backfire.
And a couple of data points have already emerged suggesting that while the Kremlin is seeking to play her, Sobchak is also playing her own game.
By framing her candidacy as a vote "against all" -- an option that was actually on the Russian ballot in the 1990s but was removed during Putin's rule -- Sobchak is lowering the threshold for claiming a moral victory.
She knows, of course, that she is not going to win. But Russian elections are not about the results, which are preordained. They're about the ritual, the optics, and the story.
And as somebody who has spent her life in the media spotlight and who certainly knows how to put on a show, Sobchak could be uniquely positioned to spoil the Kremlin's narrative and spoil its legitimization ritual.
Whether or not she is able to do this, however, largely depends on how she interacts with Navalny, who has been derisive in the past about Sobchak's potential candidacy.
In announcing her candidacy, Sobchak sent a pretty clear message that she was not interested in being used as a foil against Navalny, saying quite clearly that she would withdraw her candidacy if the opposition leader and anticorruption activist were allowed on the ballot.
But Navalny is, of course, currently in jail for organizing unauthorized street demonstrations and has been unable to publicly react to Sobchak's announcement.
But he is due to be released this weekend -- and the dynamic between the two going forward should prove fascinating to watch.
If they act in tandem (Sobchak on the inside and Navalny on the outside), they could create a powerful force that could -- while not threatening Putin's reelection, which is a foregone conclusion -- severely damage the Kremlin's narrative and undermine the regime's legitimacy.
If they operate at cross purposes, they will play right into the Kremlin's hands.