Donald Trump's vice presidential pick sat down for an interview with The Federalist way back in 2021 -- which, of course, is surfacing anew right now -- and he shared his thoughts on folks choosing to not have kids ... and what conservatives can do to change their minds.

As Vance put it ... Republicans need "to go to war against the anti-child ideology that exists in our country," and from the sounds of it -- his words may have been geared toward women ... that's certainly how many are taking it anyway.

In other resurfaced back-and-forths the Ohio senator has had online -- he recently seemed particularly rattled by journalists who were apparently encouraging others on Twitter (now X) to not have kids ... and even asking those who had children to share their regrets.

Vance slammed that rhetoric as "pathetic," as he felt the journos shouldn't have been encouraging their peers to not have kiddos. As he argued ... people with kids actually have "more meaningful" lives, which is why he's so dead-set on waging war on the ideology.

Vance also brought up his sister, Lindsay Lewis Ratliff, as an example ... as he explained his sis had previously questioned if she became a mom at too young of an age.

He added ... "People like my sister should not feel like the cultural messaging is 'your life is inadequate?' The people who are sending that message should feel that their life is inadequate. And of course they do. They’re just too ashamed about it to talk about it."

This isn't the first time Vance has attacked childless peeps in the press. He recently faced backlash for comparing Kamala Harris and other Democratic leaders to "childless cat ladies" ... which prompted a strong reaction from the likes of Jennifer Aniston and others.

He made similar statements in a 2020 podcast interview, where he accused childless people of being sociopathic.