Who is obligated to live in a Sukkah?
Women: Women are exempt from dwelling in the Sukkah as it is a time bound Mitzvah. However if they desire to dwell in the Sukkah they may do so even with a blessing. However a man may not repeat the blessing of Leishiv for the sake of women, being that they are not obligated in the Mitzvah and is thus considered like a blessing in vain.
Children: Children which have reached the age of Chinuch are Rabbinically obligated to be educated to eat in the Sukkah. This is defined as when the child no longer needs his mother which is generally from six years old. If the child is sharp and advanced to the point that he does not need his mother even before six years old, then he is obligated to be educated in the Mitzvah of Sukkah. It is the fathers obligation to educate this child to dwell in the Sukkah and if he sees him not doing so he must protest his actions and enter him into the Sukkah. However the mother, and others, are not obligated to educate the child to dwell in the Sukkah and she may even present him a meal outside of the Sukkah so long as she does not tell him to eat outside the Sukkah.
 However Biblically a child is exempt from Mitzvahs until 13 years old. [ibid]
 The reason: The reason why if a child needs his mother he is exempt from being educated is because his mother is exempt from eating in the Sukkah and therefore since he needs his mother he therefore is also exempt from being educated. [ibid]