Why is write duplicating text in parent process?

Question

I am reading Operating Systems Three Easy Pieces. While working through one of the exercises, I encountered an interesting behavior related to the 'write' system call. The program is as follows,

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <fcntl.h>
#include <sys/wait.h>
#include <errno.h>

int main() 
{
    int fd = open("./some_file.txt", O_CREAT | O_WRONLY | O_APPEND, 0777);
    int rc =  fork();
    if (rc < 0) 
    {
        printf("Fork failed\n");
        exit(10);
    }
    else if (rc == 0) 
    {
        write(fd, "the sun shines so bright\n", 26);
    }
    else
    {
        wait(NULL);
        int e = write(fd, "it's a cold night outside \n", 36);
        if (e == -1)
        {
            printf("error writing to fd, %s", strerror(errno));
            exit(-1);
        }
    }
    return 0;
}

As the parent process waits for the child process to finish, the output of this program is,

the sun shines so bright
it's a cold night outside

which is expected. However, if I change the # of bytes to write in child process from 26 to 36,

write(fd, "the sun shines so bright\n", 36);

the output changes to

the sun shines so bright
it's a colit's a cold night outside

_________^ 10 bytes

The child process string (the sun shines so bright\n\0) is 26 bytes. The additional 10 bytes are causing this behavior. I have tried different values for the write statement in child process and the behavior is consistent. Can someone please explain why this is happening?