Don't have to worry too much if your babies are over 28 weeks. Mine were 4 and 2 pounds respectively when they were born in 31 weeks. They are almost four years old now. The 2 pounds one seems more clever than the other one. In Hong Kong the government will arrange the small underweighted babies to the early training centre where there are different kinds of professionals e.g. physiologist, speech therapist, occupationist etc. to look after the babies. May be you can check with your hospital.
Don't worry too much about your babies. One of my babies were only 4 pounds when he was born and he was in ICU for 10 days. But he catches up very quickly and now he is even heavier than his brother. :)