I find that nectarines are more like peaches. I've fed them to my boy before, in small amounts(about dime sized) to no ill effects. I just make sure it's more ripe when I feed him, as the stores tend to sell them when they're a bit crunchy.
Apricot, I'm not sure. But if you want to try it, I don't see a reason not to(unless someone else knows), as it too, is similar to peaches. Just try it in small amounts, and observe.