A study found that a pair of right-handed couples are only about 9.5% likely to have left-handed children. If one of the parents is left-handed, the probability of the child being left-handed rises to 19.5%. If both parents are left-handed, the probability of the child being left-handed is 26%. 
It is observed that once children form the habit of using their left or right hands, it is difficult to change them.
 the researchers believe that the habit of using left and right hands is genetically affected.