Ivanka Trump walks out to speak  during a campaign event in Bethpage, N.Y., on April 6. (Jabin Botsford/The Washington Post)

Note to readers: This post is from April; get the latest from the final 2016 presidential debate here.

Here's Donald Trump's latest organizing embarrassment: Two of his adult children did not know they had to register as Republicans more than six months ago to vote in New York's April 19 Republican primary.

"They were, you know, unaware of the rules, and they didn't register in time, so they feel very, very guilty — they feel very guilty," Trump said during a telephone interview with Fox News' "Fox and Friends" on Monday morning.

One of the hosts commented: "Oops."

Trump said that he understands the mistake and that it's "fine" that his children Ivanka Trump and Eric Trump, who are not affiliated with a political party, did not register as Republicans in time to participate in the upcoming primary — although he joked that he might cut off their allowances. Another of Trump's grown children, Donald Trump Jr., is registered as a Republican.

New York has some of the most restrictive voting laws in the nation. To vote in the upcoming GOP presidential primary, voters had to register as Republicans by Oct. 9. Still, most presidential campaigns make an effort to educate their supporters about such deadlines.

Several recent polls have shown Trump far ahead of his rivals, Sen. Ted Cruz of Texas and Ohio Gov. John Kasich, in New York. A Fox News poll released Sunday showed that 54 percent of likely Republican voters support Trump, with 22 percent for Kasich and 15 percent for Cruz.