Lisa--
What you describe strikes me as....let me see if I can explain it..... It reminds me of a child who plays with baby-dolls - and then treats the new dog as a baby-doll, too - pushing him around in a stroller and tying bibs around his neck.
It sounds like the two boys have been "the baby"...and parents K and M can't seem to move past that role. Maybe they really can't see their babies as anything else?
Rather than confronting them - K and M probably need to see their baby doing something age appropriate for themselves. It might be a moment of realization for them. Maybe you can say "Look! Alex has been working really hard on this - he wants to show you that he can ________________."
