Most presidents have politically troublesome relatives: Jimmy Carter had colorful brother Billy, Bill Clinton had brother Roger, and the George Bushes had son/brother Neil, who was involved in both the savings-and-loan scandal of the 1980s and Asian "sex romps" that emerged in a messy 2003 divorce.

Obama has a passel of half-siblings, but his requisite nettlesome relative may turn out to be an uncle, Onyango (Omar) Obama.

In August 2011, Uncle Omar was pulled over in Framingham, Mass., for driving under the influence. His arrest revealed both several outstanding orders for his deportation and his relationship to the president. Shortly after the arrest, Uncle Omar reportedly told the police, "I think I will call the White House." In November 2011, just as the 2012 election was kicking into gear, the White House told The Boston Globe there was no record of Obama ever having met Uncle Omar.

On Tuesday, at a public immigration hearing, Omar Obama casually disclosed that not only had President Obama met him, but had lived with him for about three weeks in the 1980s. On Thursday, the White House issued a correction, confirming that the president stayed with Omar briefly when he moved to Cambridge to attend Harvard Law School. "After that, they saw each other once every few months, but after law school they fell out of touch," said White House spokesman Eric Schultz. "The president has not seen him in 20 years, has not spoken with him in 10."

Later on Thursday, White House Press Secretary Jay Carney explained away the White House's changing story on Uncle Omar, saying nobody had bothered asking Obama about his uncle until this week:

This is embarrassing for the Obama White House. But it could also complicate one of Obama's big goals of his second term: Immigration reform.

Bearing a student visa, Onyango Obama arrived in the U.S. in 1963 to attend boarding school. Once the visa expired in 1970, Obama continued living illegally in Massachusetts — including while Obama lived with him, preparing for law school — until Tuesday. At this week's immigration hearing, Judge Leonard Shapiro granted Uncle Omar legal residency, citing his good moral character and a federal statute that grandfathers in some immigrants who came to the U.S. before 1972.

Uncle Omar got his green card just as his nephew is making a renewed push for a comprehensive immigration reform bill sitting idle in the House. In a Thanksgiving week speech in San Francisco, Obama signaled he is open to splitting the bill into individual parts, as House Republicans want. There has been growing optimism that immigration reform might actually get done in this do-nothing 113th Congress. This won't help.

The White House says Omar Obama was granted legal residency "without any interference from the president or the White House," notes New York's Joe Coscarelli, wryly adding: "As if the heads of those inclined to believe otherwise hadn't already exploded in rage."

It's safe to say that many conservatives aren't buying the White House's explanation. "If you believe Jay Carney, the original denial was issued based on documentary evidence," says Daniel Greenfield at FrontPage. "Also if you believe Jay Carney, the moon is made of pure hopium and so is Barack Obama." Hot Air's Allahpundit is only a little more polite:

Who are you going to believe? A man who cheated to stay in the U.S. illegally, or the president of the United States? Right. Believe the illegal. [Hot Air]

Why does that matter? House Speaker John Boehner (R-Ohio) needs a sizable number of conservative Republicans to take a leap of faith that immigration reform will be good for the GOP, if not the country. If enough conservatives believe that Obama is gaming the system to pull in his previously undocumented Kenyan-born uncle, that will make voting for any immigration reform that much harder of a sell.

If a minor episode of White House crow-eating over President Obama's absentee father's half-brother seems an unlikely event to derail a major piece of legislation, it might well be — at least by itself. But conservatives were already wary about the same immigration judge's decision to grant asylum to Obama's aunt, Zeituni Onyango — Uncle Omar's sister — in 2010. And Uncle Omar has been nominated as a symbol of Obama's immigration policy before. Here's Tom Fitton, president of the influential conservative group Judicial Watch, a month after Oyango Obama's 2011 arrest:

President Obama's "Uncle Omar" is the face of what is wrong with the Obama administration's lawless and dangerous approach to illegal immigration. Instead of being deported, as the law requires, Uncle Omar was allowed to roam the streets and endanger the lives of innocent people, including a law enforcement officer. [Judicial Watch, via WND]