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The siblings earned their riches with the sale of their company Frac Tech for $3.5 billion in 2011

Together, their donations give Cruz and his allies more money than any other Republican except Jeb Bush

Washington CNN  — 

Two low-profile Texas brothers have donated $15 million to support Sen. Ted Cruz, a record-setting contribution that amounts to the largest known donation so far in the 2016 presidential campaign.

Farris and Dan Wilks, billionaires who made their fortunes in the West Texas fracking boom, have given $15 million of the $38 million that the pro-Cruz super PAC, Keep the Promise, will disclose in election filings next week, according to sources outside the super PAC with knowledge of the giving.

The siblings earned their riches with the sale of their company Frac Tech for $3.5 billion in 2011, and since then have shuffled large contributions to the leading social conservative nonprofit groups that aren’t required to reveal their donors. But they will no longer be able to avoid detection after giving a historically large and early donation that now make the brothers two of America’s most prominent political donors.

“Our country was founded on the idea that our rights come from the Creator, not the government. I’m afraid we’re losing that,” Farris Wilks, a 63-year-old pastor in the small town of Cisco, said in a statement to CNN. “Unless we elect a principled conservative leader ready to stand up for our values, we’ll look back on what once was the land of opportunity and pass on a less prosperous nation to our children and grandchildren. That’s why we need Ted Cruz.”

Keep the Promise is technically four separate committees that give three families more control over their own super PAC. Most of the attention has focused on Robert Mercer, a New York hedge fund magnate who gave the second-most money to conservative groups in 2014 than any other Republican donor. Mercer has given $11 million of the $38 million raised, according to a leader of the super PACs. Another $10 million comes from Toby Neugebauer, a Houston investor and a personal friend of Cruz’s. The involvement of the Wilks brothers was first reported by National Review.

READ: First on CNN: Cruz super PAC’s plan to win presidency

Together, their donations give Cruz and his allies more money than any other Republican except Jeb Bush, a surprising achievement for a firebrand senator more embraced at a Tea Party rally than at a black-tie business gala.

Friends and associates of the Wilks brothers say they are unaffected and unassuming, depicting them as hometown-loving Texans who morphed into billionaires over the course of a decade. Intensely private, those close to the pair say they are nervous about the spotlight that will shine on their church and their family thanks to the donations.

“If Dan and Farris walk into a room, they don’t want ever to be known, to be announced. They just come in and sit in the back,” said Luke Macias, a Texas political strategist who has worked with the family. “They are normal people. They dress normal. They show up normal.”

Several other Republican donors will make seven-digit contributions to super PACs, which can accept unlimited donations, that will dwarf sums recorded in 2012: Norman Braman, a Florida auto dealer, will reportedly give up to $10 million to Marco Rubio’s. Several Jeb Bush supporters are expected to have given $1 million to his and to be eager to give more. But the Wilks family’s $15 million donation – split between two people – is likely to be the largest gift to a candidate on next week’s reports.

Unlike some other mega-donors with an affinity for the ideological slugfest, the brothers shun giving that is meant purely for firepower in partisan fights. They choose specific projects over broad platforms. Through their $100 million family philanthropy, The Thirteen Foundation, the brothers gave nearly $19 million as part of their tithing to religious and conservative nonprofit groups like the Family Research Council and Online for Life in 2013, according to the most recent tax filings.

Driven mostly by their opposition to abortion and their fear that their religious sect – which interprets every word of the Bible literally – is under attack, Dan and Farris Wilks have slowly become more accustomed to funding campaigns. As recent billionaires, however, they haven’t yet risen to the profile of the other conservative siblings that have revolutionized outside spending: the Koch Brothers.

Now, though, they are prepared to step right into the middle of a potentially nasty Republican nomination fight that could cost hundreds of millions of dollars.

“We need a true leader in Washington,” Farris’ younger brother, Dan, 59, said in the statement. “A leader that will stand up for biblical morals. We need a leader who is proud of America, not one who apologizes for us. We need a leader who encourages hard work, not one who tells people who don’t work that they should make the same living as people who do. We need a leader who will make sure America doesn’t end up a socialist nation.”

Born to a poor family that once lived in a former goat shed, Farris and Dan Wilks spent their careers as brick-builders with their own masonry business. In 2002, they founded Frac Tech, which became one of the best positioned companies to capitalize on the growth of fracking, a controversial practice that involves the removal of natural gas or oil from rock formations.

Slowly, they marched toward a bigger role in the fracking industry. When competing Texas frackers looked to freeze the brothers out from the companies that distribute the sand needed to drill, the siblings opened their own sand quarry to thrive. Just as the West Texas fracking business began to boom, the brothers invested in their own line of trucks and became some of the largest fracking truck-producers in the country.

In 2011, they cashed out – and began to buy enormous amounts of land in Montana for elk hunting and fly fishing. As of last year, they owned more than 310,000 acres of land in the state, making them Montana’s largest private landowners, according to The Billings Gazette.

Today, Forbes pegs their net worth at about $1.4 billion each.

At the heart of their life, still, is the Assembly of Yahweh, which preaches a mix of Christianity and Judaism and holds the Bible as infallible. A different Wilks family member gives a sermon many Saturdays. Last week, it was Farris’ turn.

“He was a pastor before he was a billionaire and he continues to pastor after being a billionaire,” said Mat Staver, a prominent conservative activist close with the family.

It is not yet clear how the brothers plan to spend their money in the Cruz super PAC, or whether any strings are attached to the $15 million contribution. But the pair are said to have a particular desire to fund breakthroughs in social media and digital organizing, eyeing long-term opportunities to mobilize Christian voters on emerging or created-from-scratch platforms online.

Much of their giving is directed by Jon Francis, a family son in-law who heads The Thirteen Foundation, but those who have pitched projects to the brothers say that their philanthropy is very much a family affair. It is not uncommon for entrepreneurs to face questions from a half-dozen Wilks family members when asking for money.

RELATED: Bush raises over $100 million to help his campaign

That includes Republican presidential candidates. The brothers have been familiar with Cruz since he used the office of Texas solicitor general to launch several high-profile legal fights to defend Christian causes. But other Republican presidential candidates, aware of the Wilkses’ net worth, have nevertheless courted their checkbook. The candidates most aggressively pining for their support, according to multiple people familiar with the outreach, were Wisconsin governor Scott Walker and former Arkansas governor Mike Huckabee.

The Wilks family’s eventual pledge to Cruz was driven by his emphasis on preserving Christian organizations’ ability to operate amid cultural victories for the left. But it was also motivated by the Texas senator’s ability to speak about policy in the entrepreneurial terms that the brothers use when evaluating projects.

“One of the pleasures of doing business with them is they kind of treat like you like you might be the next Wilks,” said Jeremy Boering, a California filmmaker who has successfully won grants from them.

Boering said that’s the philosophy that Cruz pitched to Farris Wilks – and why he’s funding him.

“He thinks he’s one of the only guys in the movement that seems to authentically wants to preserve the market, authentically preserve the way of life that allows people to move from bricking walls to being a billionaire,” Boering said.