Is it necessary that the size of all elements in a union should be same?

struct emp
{
    char *n;
    int age;
};
struct emp e={"CuriousTab", 15};
FILE *fp;
fwrite(&e, sizeof(e), 1, fp);

typedef struct s
{
    int a;
    float b;
}s;

#include<stdio.h>
#include<malloc.h>

struct emp
{
    int len;
    char name[1];
};
int main()
{
    char newname[] = "Rahul";
    struct emp *p = (struct emp *) malloc(sizeof(struct emp) -1 +
                    strlen(newname)+1);

    p->len = strlen(newname);
    strcpy(p -> name, newname);
    printf("%d %s\n", p->len, p->name);
    return 0;
}

/* sample.c */
#include<stdio.h>

int main(int argc, char **argv)
{
    printf("%s\n", argv[argc-1]);
    return 0;
}