I think Fringe is one of the smartest shows on TV. They're juggling a freaky premise (two alternate universes are trying to survive under the shadow of possible demise) and some subtle character work at the same time.
But the multiverse they've constructed assumes that for every person 'here', there's an exact duplicate 'there'. Same looks, same age, same name. That makes it fun for the actors, most of whom get to play alternate versions of themselves. But that also presupposes that every couple has their children at the exact same time… and has for all of history. If any one person has a different set of offspring anywhere in history, the entire doppelganger concept falls apart.
In the recent episode "6B", the climax relied on the situation of an elderly couple having children in one universe, and no children in the other. In fact, they had at least two, since they were referred to as "the girls". Uh-oh! The entire construction of this multiverse may be faulty!
But wait. The Walter from 'here' broke into 'there' to steal Peter. That, theortically, means that everything from that moment on (in 1985) is up for grabs. Children born after 1985 wouldn't necessarily have doppelgangers.
In the episode, the old woman claim to have been with her husband since they were 20, and said they were together "almost 45 years". That means she's almost 65. 1985 was twenty-six years ago, when she was almost 39. She might have had two children (even twins) at such an age.
Bullet dodged! All is right with the multiverse!
Of course, I haven't dodged the bullet of excessive geekiness. But that's okay, too. That ship sailed long before 1985.