Creating a new user in CygwinCygwin users are tied to the users in Windows. Therefore, use the following command to first create a new user in Windows.
net user NewUserName NewUserPassword /add /yes
Replace NewUserName and NewUserPassword with actual values.
Then, associate this user with a local group on Windows using the following command.
net localgroup AnExistingGroup NewUserName /add
Type net localgroup by itself to get a list of local groups.
Then, use the mkpasswd command in cygwin to add this user in the /etc/passwd file.
mkpasswd -l -u NewUserName >> /etc/passwd
Finally, create a home directory for this user in /home/ folder.