How to copy a tree in C

struct node
{
...
int num_number; //number of children nodes
node **children; //pointer point to children nodes. When I copy the node, how can I deal with **children? Right now, there is no children yet.
}
void copy_tree(node *node, node *T)
{
    int i;
    char number[12] = {0}; //used in case of if
    int n = node->num_children; 
    if (node == NULL)
        T = NULL;
    if（...)
    {
        .... // copy the node
    }
    else
    {
                ....  // copy the node
    }
    for(i=0; i<n; i++)
        copy_tree(node->children[i], T->children[i]); // I want to copy the children nodes recursively, but the new node has no children; that is T->children not existing, how can I copy the children nodes and allocate to parent?