Twins?

I took the Lambs to the pool today. There were several other families there on this hot day. A couple of boys were convinced that Lamb 1 and 2 were twins because they have the same swim shirt. When I told them that all the Lambs are 2 years apart, the mom replied that they all look so much alike that she was trying to figure out if they were triplets. When she heard they were 2 years apart she told her boys that my boys were probably ages 8, 6, and 4. She was correct except we don't have a 4 year old, we have a 10 year old.
Lamb 1 and 2 wear the same size shoes. Lamb 1 likes his clothes to fit tight, Lamb 2 likes his clothes to be baggy. If it wasn't for that they could wear the same size clothes too. Often when Lamb 1 outgrows his clothes they are too small for Lamb 2. Then there is Lamb 3 that looks 2 years younger than he is because he is so skinny.
My MIL said she was often asked if her boys were twins or triplets. They had closer spacing than we did. I was asked that a few times when we just had Lamb 1 and 2. I did not expect to be asked that now.
The Lambs have their annual checkups scheduled for the end of August. I am curious what their weight and heights are and how it compares to other boys their age.