"I have to meet my nephew at eight o'clock."
Translation:Je dois retrouver mon neveu à huit heures.
What is wrong with "Je dois rencontrer avec mon neveu à huit heures" ?
"Rencontrer avec" is incorrect.
"Rencontrer quelqu'un" suggests you have not met before.
Since you are supposed to know your nephew, the best verbs to use can be "retrouver" or "rejoindre" to mean "meet someone somewhere".
what about rendez-vous? as in "je dois rendez-vous avec mon neveu a huit heures" Forgive me if it's a dumb question
Can I use "rendezvous"?
"Rendevous" is an anglicised word, often used as a verb.
It is derived from the French masculine noun rendez-vous which means "appointment or meeting" in a professional sense or "meeting, date" in a social sense.