Brotherly love

Question
We have 2 male cats who are brothers and are now just over 3 years old. Recently one of them went missing and the remaining cat was pinning for him and constantly crying for him. 5 days later the other cat returned and now his brother is very off with him, hissing and growling and generally stalking him around the house. His brother can't understand this agressive behaviour. Any tips on why this may be happening and how/if we can get them to get on with each other again?

Answer
Stewart,

A cat goes by smell and not by sight recognition. The cat that was missing came home with different smells on him and the brother thinks he is a different cat.

As he licks himself he will replace his own smells. Though I've never tried it I've heard people have good luck in that situation by putting a tiny drop of vanilla on each cat's forehead so they smell the same. Also rubbing the non-missing cat with a towel and then rubbing the cat that came up missing with that towel helps.

Keeping them separated and doing introductions like they were new cats meeting may be necessary, but the problem should resolve itself in a few days when the missing cat smells like himself again.

Tabbi