Because they are preemies, the boys may develop more slowly than their chronological age peers. They are 4 months but may only exhibit milestones of 2 month olds.
So far, they are doing pretty well. They are meeting most of their physical milestones for their actual age. Smiling and some of the cognitive development is closer to their adjusted age.
But..they are really starting to smile and laugh and I love it. Makes me want to do nothing but make silly sounds and faces simply to get a smile or giggle :)