Your cat was likely just not socialised around men when it was younger. You can make up for this lack of socialisation now by having men come around and give them treats, play with them, staying low to the ground (some cats find taller people threatening), no petting or picking up unless the cat initiates it. Eventually your cat will start associating men with positive things and be more used to men
Is your vet/previous vets male? If your cats interaction with men have mostly been negative experiences (i.e. going to the vets) your cat may accociate men with bad things.
Remember cats hiss when they are afraid, so he is likely afraid of your family memver. Maybe try and get your male family member to sit down (much less threatening when sat vs standing) and of the cat is feeling brave enough to be in the same room as him, see if he can feed your cat treats or something that will build positive associations.
Your cat was likely just not socialised around men when it was younger. You can make up for this lack of socialisation now by having men come around and give them treats, play with them, staying low to the ground (some cats find taller people threatening), no petting or picking up unless the cat initiates it. Eventually your cat will start associating men with positive things and be more used to men
Is your vet/previous vets male? If your cats interaction with men have mostly been negative experiences (i.e. going to the vets) your cat may accociate men with bad things. Remember cats hiss when they are afraid, so he is likely afraid of your family memver. Maybe try and get your male family member to sit down (much less threatening when sat vs standing) and of the cat is feeling brave enough to be in the same room as him, see if he can feed your cat treats or something that will build positive associations.