Introducing new cat to resident kitten?

It is good that they come from the shelter where they are used to other cats.

The biggest problem is that they are different ages so will have different food needs. I would feed them the same adult cat food but give the kitten canned kitten food 2 x a day.

For introducing them, the new cat must be kept in a bathroom or bedroom for 2 weeks, the will sniff paws under the door. After that you can let them out together but only when you are home and keep separate at night or when you are away until you are sure they are okay.

http://therealowner.com/cats/introducing-a-new-cat...

Get a see through or wooden baby gate. Place your small kitten in a closed off room, and of the other cat on the other side of the gate. Let them get to know each other. After they seem to be acquainted with each other, remove the gate and move them to a small room WITH SUPERVISION. cats might now get a lot well at first.

If you can, barricade one of the animals in the bathroom/laundry room with a baby fence or something alike. That way they can start to get used to each other without any direct altercations. Make sure you monitor them while you do this. If you feel like they're getting along, put them both in the barricaded room but don't take your eyes off of them! After a few days/weeks they should be fine if neither of them are aggressive in any way. Unless you are watching them, keep them separated (ex. you're at work, keep one of them locked up in a safe room with their food/liter box and such) so that way neither of them can harm each other. Good luck!

feed them in separate rooms with the food bowls on different sides of the door. start far apart then slowly move the food bowls closer. this way they have to positive association of food with each other's scent.