All praise is due to Allah alone, and may the Salah and Salam of Allah be upon our Prophet Muhammad, his family and his companions. To answer your question, we say while seeking the success from Allah: You need to be kind and nice with this person and encourage him to stay a Muslim. This person is considered a male since he was originally a male before the sex change operation that he had to remove his private member. That being said, he should be advised to stop taking the hormones that stimulates the development of female characteristics, and to explain to him that he needs to restore his original male characteristics, and help him along the process while being patient with him. In regards to not accepting him among men, if that is because you fear you will be tempted or enamored because of his current status, then you should be cautious while dealing with him so that you do not end up enamored or tempted because of him. This is similar to the case that scholars talked about regarding the ruling on handshaking a beardless and handsome man. In spite of all that, you cannot prevent him from praying in congregation or praying Friday with men. You have to advise him nicely to refrain from anything that may tempt men be it related to his dress code or behaviors. Your brother, Khalid al-Mosleh, 9/11/1428 H.