Like P'Gell, I never had multiples until I hit my 30's. (Hell, I didn't even orgasm on a regular basis for quite some time!) I haven't had kids though.
What works for me is to make sure my clit doesn't get over-stimulated and overly sensitive. I still need stimulation there to orgasm, though, just not too much. Then for my second (and third, fourth, fifth, sixth, etc.) I like to focus mainly on internal g-spot stimulation until I'm inches away from orgasm, and then toss in just a bit of clitoral stimulation to push me over the wall.
I'm not sure that it's something everyone can do, but just because you can't do it now doesn't mean you won't be able to do it later - if that makes sense. Your body is constantly changing, and as long as you keep experimenting you'll continue to learn with it what it's capable of.