My two-years-apart twins

Ben had his 6-month well-baby check on Wednesday and he is perfect, just as I suspected.  He tipped the scales at 17 pounds 15.5 oz and was 27 1/4 inches long.  For comparison, Dan was 17 pounds 15 ounces and 27 inches long.  Pretty much identical, just like at four months.  But just how identical are they?  Here are two pictures of Dan from March 15, 2009, followed by two pictures of Ben from March 4, 2011.  I think it's obvious that they are brothers!