What to you and your spouse is a “normal” argument, to your toddler and bigger child, it seems like the end of the world. The two people that your child loves most in the world are really angry and shouting at each other and it is scary! Your child might even think that he is to blame for you and your spouse fighting.
Even if you and your spouse make a habit to fight in private, away from your child, the tension in the atmosphere will definitely be felt by your child and be just as scary to him. The best thing to do with toddlers and small children is, once you and your spouse are done fighting, then make a point of reassuring your child that you still love him and each other as well.
Small children do not have the emotional capacity to deal with their parents fighting. All they know is that mom and dad are supposed to love each other, so why are they being so ugly towards one another? They just do not understand that sometimes people, even those who love each other tremendously, do have differences and do argue about them - to the small child it is simply very frightening.
However, it has also been found that children who have not witnessed their parents fighting have been totally devastated when their parents decided to divorce. The children were absolutely unaware that there was any disharmony between their mother and father. To the children, their family life was perfect. When the parents finally divorced though, that perfect life fell apart at the seams for the children.