advice for introducing adult cats to each other?

[gubeedal]

My fiance and I have two female cats. Both were adopted from a shelter as adults.

My brother's ex-wife left her two male cats with him telling him "I'll be back for them". That was five years ago. Well, his new spouse is pregnant and they are both allergic to the kitties and he has been trying to find them a good home for awhile now. While he really doesn't want the cats, he still wants to know they are being well taken care of.

My fiance and I have a very large house and no kids. We thought we might try to take his cats in. Any advice on introducing the set?
Almost forgot... All kitties are fixed.

 

[Elaine M]

Do a slow introduction--keep the new ones in a separate room with the door closed (their own bowls and litter boxes) for a week, changing out which cats have the run of the house for a while, and then after a week introduce ONE to the current pair by opening the door to have one of them come out. Be there to supervise. Put that one back in and let the other one come out a few hours later, supervising how they react with each other.

With luck it'll all be anticlimatic. Do not force any of them to 'see' each other.