President Barack Obama revealed on Saturday that his children helped him understand why embracing civil unions was not the same as endorsing marriage equality.

Obama came into office supporting civil unions, but it wasn't until 2012, with a little nudge from Vice President Joe Biden, that he came out in favor of same-sex marriage.

The president said that he initially didn't think the labels for same-sex couples really mattered as long as they had the same rights as heterosexuals. Sasha and Malia helped him see why that wasn't the case.

"I have to confess my children generally had an impact on me," he said during a town hall in London. "People I loved who were in monogamous same-sex relationships explained to me what I should have understood earlier, which is it was not simply about legal rights but about a sense of stigma, that if you're calling it something different it means that somehow it means less in the eyes of society."

Obama described the marriage equality movement as "the fastest set of changes in terms of a social movement that I’ve seen." He also praised activists for reaching out to those who didn't initially support marriage equality and framing the debate for them as one about "family values."

The president has faced questions about LGBT equality in the U.S. during his trip to England, after Britain issued a travel warning for lesbian, gay, bisexual and transgender travelers to North Carolina and Mississippi, which recently passed discriminatory laws. Obama said on Friday he believes North Carolina's bathroom law should be overturned. However, he stressed on Saturday that he would need the support of Congress to block the states from passing such laws -- which he noted was unlikely to happen.