Fighting like cats and dogs.

No, not the children, they (mostly) get along very well. When we moved here there were several barn cats. Some dogs and cats get along, others merely tolerate each other, some fight. Ours fall into the last category. There was one remaining barn cat and she had a litter of kittens somewhere in the barn. Tragically, she was killed. The children found and extricated the kittens from between the floor joists in the barn. They fed them every four to six hours, even getting up in the night, for two weeks until I located a foster home. From the foster home they will go to adoptive homes. It was sad but for the best.