Thank you for contacting Justanswer.com.
It does appear that your authority is being undermined by others. The employer has no legal duty to provide you with support, although that typically makes good business sense.
Unfortunately, you would normally have no legal recourse against the employer if the circumstances do not change and it may be best to look for other employment.
Unless you have an employment contract, you would normally be an employee at will and the employer can terminate you without notice and without good cause.
It may be that the new employee knows people within the organization and you are seeing the results of that. However, nepotism is not prohibited by law with regard to private company's typically, so other than complaining to HR, you have few options unless you wish to retain a local employment law attorney to aid in attempting to resolve the situation.
Good luck and take care.
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