Little ones are naturally curious especially when they notice differences. They see a womans chest, its very different from theirs and its very nice and soft to touch. They really have NO idea about sexuality at the age of 4. Best thing to do is to just tell them no, it isnt nice to touch there. Never over-react and act like its a huge deal because it isnt - at least to them. Some little ones
while we are at it we should tell them not to jump on guy's lap.
we get hurt too :( I mean pain beyond imagination.