Cat attacking guests

I have two cats, in the last year my male cat started hissing at people when they come over..  He runs up to them to sniff them and when they go to pet him he swats and hisses at them.  He also sometimes blocks people in rooms and wont let them out.   He also attacks my female cat but he is very loving to my husband and myself, he lets us pet him and pick him up.  I don't know what to do.    We recently went away and he hissed at people that came over to feed him.  Help...

Thank you.