cod, it's really not your uncleanliness! Kids often pick them up from school/nursery situations especially where there are things like sandpits.
They scratch their bums, then everything they touch gets the worm eggs on (so door handles, carpets, sandpits etc.), someone else gets the eggs on their hands from touching the eggs and they touch their mouth and little worms hatch in their tummy!
Last time dd got them, we all got them (it was a lovely, family bum scratching time). Are you sure the other dss don't have them?