it's all quite vague.
Exactly! Plus in the original backstory Jeremiah is years and years older than Barnabas. And it all takes place in the 1830s, so we'd have to forget that and transport it ourselves to the 18th century - and it was bad enough when the show retconned events 40 years earlier and threw out everything we were led to believe!! We shouldn't have to do so nor should we be able to do so just to make some sense of vagaries!! It makes everything a complete mess!! Which is why it's so much simpler to accept what the show went out of its way to establish: that what we were led to believe in Eps #1 through #365 never happened the way we were led to believe it happened, and, therefore, it's so much simpler to interpret Laura and Jeremiah's marriage through what we actually saw in 1795/96, meaning that if Barnabas first saw Laura when he was ten, then she wasn't yet married to Jeremiah because he was also ten - and when Laura speaks of Barnabas as a child, she wasn't much older than he was. And it is quite possible to do all that because nowhere does anyone state plainly that Laura and Jeremiah were already married when Barnabas and Laura first saw each other...