it should go without saying that our hands are full. yes, I mean it should go without saying. we've heard it before and sadly will hear it again. really though, you should see how full our hearts are!
my reproductive life is really not your concern. yes, we know what causes it and apparently some of us are better at it than average...
if each child has the same father is also not your concern.
now some suggestions.
if you see a larger family out and the children are not screaming at the top of their lungs and running all over the place, compliment the parents. you may not see the children doing those things but I guarantee you that it feels like they are to the parents. parents get outnumbered and it's draining trying to keep reigns on them all. let us know we're not failing and that you noticed, it will do wonders for those parents.
if you are a friend or relative of a family with more than a couple children. invite them over. really, they get left out of a lot. no, you don't have room, invite anyways. or even offer to watch the children once in a while. once a year is fine. really, it's rare for parents of many to get time out together sans children.
don't assume that they need all your hand-me-down clothing but do feel free to ask as much of the time it is very appreciated.
most of all remember that they are a family. they are real people and not freaks to be gawked at and commented on. maybe you should try admiring them because we get told all the time that you couldn't do it ^.~