If Your Brother Jumped Off A Bridge, Would You?

I am getting really tired of the monkey see monkey do that goes on between Jack and the babies. He says a "naughty" word (like stupid, fart, poop, etc) and they repeat it. Jack didn't say those words when he was their age, but thanks to him I have 2 year olds that talk like 5 year old boys. He hits himself in the head and they do the same. It makes me absolutely crazy! I try to explain being a good example, but he either doesn't get it or he just doesn't care. Yesterday took the cake. We were walking out of the gym, it was raining, and Jack started complaining about being thirsty. Of course this prompted Ben and Lauren to say they were thirsty too. We got in the car and Jack removed his shoe and LICKED. THE. BOTTOM. OF. IT. These weren't just any shoes. These were the nasty flip-flops that he wore all last summer. I am sure they have seen their share of dog shit, yard chemicals and general filth. I actually refuse to touch these shoes they are so nasty, they are crunchy from all of the foot sweat from 100 degree days last summer. Not only did he lick the bottom but then he told the babies how good the water on the bottom of his shoe tasted. Before I could say, "don't lick your shoes" Ben and Lauren had their shoes in their mouths. I can only imagine the germs they have ingested. I just hope it strengthens their immune system rather than makes them sick!