What they’re doing, are they walking, crawling babbling etc. but I’d imagine they would catch up. This whole babies and kids need to be socialized is 20th century pseudoscience. Kids stayed home, worked the farm, maybe got together with other families after church if you lived close enough to town to make it every week etc. You were pretty much surrounded by only family back then and the world was a better place. Now socialization means brainwashing.