Former Texas Rep. Ron Paul was seen but not heard when his son, Kentucky Sen. Rand Paul, formally announced his presidential campaign on Tuesday. But the elder Paul hasn’t been shy about expressing his opinions on various – and controversial – topics.

In the past year, Ron Paul has written that a violent revolution should be considered to protect individual liberties, said the secession movement should encourage supporters of freedom, and asserted that the U.S. government is “likely hiding [the] truth” about the Malaysian flight believed to have been shot down by pro-Russian separatists over Ukraine.

Several likely 2016 candidates have familial relationships that will inevitably pop up as issues during the campaign. Jeb Bush has two former presidents in his immediate family, and Hillary Clinton is married to one. Paul's GOP rival Ted Cruz's father was never elected to office but has become a min-celebrity within the GOP for his fiery rhetoric.

But unlike pastor Rafael Cruz or President George H.W. Bush, libertarian icon Ron Paul is producing a weekly column along with frequent media and public appearances that present a potential problem for his son’s presidential run.

“I have a great deal of respect for my dad, my dad is probably one of the most honest, genuine characters in American political history,” Paul told Politico after his announcement. “We don’t agree on everything, but not everyone agrees with their dad on everything.”

But that relationship has shaped much of Rand Paul’s political identity. He has embraced many of the small government ideals that his father espoused during his three presidential runs and decades in Congress, and Rand served as a strategist on his father’s campaigns. But Ron Paul’s continued opining about the issues of the day means he will be remain an arm’s length away from his son for most of the campaign.

Here are some recent Ron Paul comments that may surface during Rand Paul’s campaign.

Secession: Ron Paul wrote last year: “The growth of support for secession should cheer all supporters of freedom, as devolving power to smaller units of government is one of the best ways to guarantee peace, property, liberty.”

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And in a conference in February, Buzzfeed reported Paul said secession is “gonna happen. It’s happening.” He has said states seceding from the U.S. and local governments seceding from states will happen “de facto” when conditions break down after, he predicts, the economy collapses.

Sen. Rand Paul, R-Ky. arrives to announce the start of his presidential campaign in Louisville, Ky., on Tuesday. In the background, upper right, are his parents, former Texas Rep. Ron Paul and his wife, Carol. Carolyn Kaster / AP

Revolution: In a column filled with his predictions for 2015, Ron Paul says Thomas Jefferson “believed the people must warn the rulers that taking up arms against the government is legitimate if the government fails to protect the people’s liberty.”

“This should be a consideration,” he wrote, before adding that violence alone will achieve nothing. “All positive revolutions must be philosophic in nature,” he added.

Russia: Ron Paul called U.S. sanctions against Russia for its incursion into Ukraine “a grave mistake,” and warned it could harm the economy at home. “I don’t think we have any business there,” he said in one of his frequent appearances on the Russian-run RT television in 2014.

“I am not pro-Putin, and I’m not pro-Russia. But I’m pro-facts,” Ron Paul said earlier this year. He also said the Ukrainian unrest was a coup orchestrated by NATO and the European Union, and not an uprising of Ukrainian citizens standing up to Russia’s influence in their country.

Rand Paul, however, wrote a forceful op/ed in Time calling for the U.S. to take strong action that would isolate Putin.

These 10 letters to NSA whistleblower Edward Snowden prove he did the right thing: http://t.co/Uil7bJTwCb #truth #freedom #follow — Ron Paul (@RonPaul) December 23, 2014

Ron Paul raised eyebrows last summer when he partially blamed the U.S. for the crash of Malaysian Airlines Flight 17, which the Obama administration believes was shot down by pro-Russian separatists. Ron Paul wrote that western media was only reporting “government propaganda” about the crash that killed 298 people.

“They will not report that the crisis in Ukraine started late last year, when EU and US-supported protesters plotted the overthrow of the elected Ukrainian president, Viktor Yanukovych. Without US-sponsored 'regime change,' it is unlikely that hundreds would have been killed in the unrest that followed. Nor would the Malaysian Airlines crash have happened,” Paul wrote in his weekly column called “Texas Straight Talk.”

In August he wrote: “Questions do remain regarding the serious international incident. Too bad we can’t count on our government to just tell us the truth and show us the evidence. I’m convinced that it knows a lot more than it’s telling us.”

The Economy: In his 2015 predictions column, Paul wrote, “Sanity will not return to U.S. leaders until our financial system collapses — an event for which they are feverishly working.” He predicts an economic crisis greater than the 2008 collapse is fast approaching.

“The poor will get poorer and the rich richer until the spirit of revolution in the people calls a halt to the systematic destruction of freedom in America,” he wrote.

Republican control of the Senate = expanded neocon wars in Syria and Iraq. Boots on the ground are coming! — Ron Paul (@RonPaul) November 5, 2014

Paris attacks: “Does anyone wonder why, after 14 years of drone strikes killing more than 800 al-Qaeda militants, it seems there are still so many of them?” Paul wrote in February.

One month earlier 16 people were killed during an attack on the satirical magazine Charlie Hebdo and a kosher grocery store in Paris. Al Qaeda took responsibility for the attacks.

“What if it is interventionist and militarist western foreign policy that is motivating people to shoot up magazines and seek to bring terrorism back to the countries they see as aggressors?” Paul wrote.

ISIS: Ron Paul called it a “glimmer of hope” when President Obama said the U.S. did not yet have a strategy to deal with ISIS in Syria.

“A new U.S. military incursion will not end ISIS; it will provide them with the recruiting tool they most crave, while draining the US treasury. Just what Osama bin Laden wanted!” he wrote in August of last year.

In March he wrote: “If we really want to defeat ISIS, the last thing we should be doing is bombing and sending troops back to Iraq and into Syria.”