How to help your kitten defecate in the absence of its mother
Usually after feeding, the mother grooms the kitten, giving special attention to the anal area. The licking aids digestion and stimulates excretion as well. So, in the absence of the mother cat you can gently massage the kitten using a warm washcloth or a piece of damp gauze in the anal and urinary area. Wash or discard the cloth immediately and dry the kitten off before putting him back in with his litter mates.
Soon after feeding, hold the cat belly down with one hand and rub its belly gently to stimulate digestion. It would also help the kitten burp and expel air in the digestive tract. At the same time it would also stimulate them to urinate.
Once they are four weeks old you can teach him to use the litter box. You can place the box next to the kitten after meals, when they wake up or drink water. When one kitten has finished using the box, put it back in with its litter and put the next one in the box. Allow each kitten a few minutes to use the box after each meal.
If you notice that any of the kittens are not urinating or defecating even after receiving help or when put into the litter box, you should contact a veterinarian right away. The kitten might be constipated or have a blockage that will need to be removed.