please dont stress!! do they have any other traits? put simply, there is a protein lacking in the connective tissue. means that things aren't as stretchy as they should be, eg skin...so stretch marks are a big thing. hyper extention and long long bones are another because when humans grow up, the ligamints are what stop the bones growing any longer itms. ligaments are connective tissue, so they don't stretch right which is why i when i put my arms out straight my elbows are at a great than 180degree angle (sorry can't remember the proper name for it). and why my brother has monkey arms =P (think about da vinci's vitruvian man - the man with limbs spread that make a perfect circle, and where a humans height is the exact same as the distance between arms spread out). people with marfans, they are out of proportion. because the arms kept growing cause the ligaments didn't tell them to stop. these things, are things that can't kill you.
lung fields are long - means they don't fit one one xray film. can lead to higher chances of pneumonia etc.. due to not sufficiant deep breathing etc..
retina detaching is due to it being held together by connective tissue. basically if anyone sees a black spot in their vision, get them to ed ASAP (this is a medical emergency).
and yea, heart, our hearts are made of connective tissue. so in terms of valves etc, that would be why your hubby's family are getting regular checkups.
I also agree with Kim, your hubby has made it this far =) it is worth getting his heart checked.
truth is i'm not sure in terms of the kiddies, if they are too young to be diagnosied etc...