The thing is take an example say your damily is having a problem X from generations now if you marry tour cousin you are giving mire chance for that problem X to grow if you marry someone out if your family you will be bringing new geens in your family and there may be a chance that the new...
well not much but i do donate to the org of save the girl child headed by my friend
and to my local save the dog foundation as it helps the street dogs to get a home and keeps the roads clean
and i also donate blood every year :)