dogsitting help

I am currently dogsitting my husband's parents dog while they are on vacation and I'm having an issue with one of my dogs getting along with him.
I have 2 dogs, a corgi and a greyhound mix who are both 2 years old. The visiting dog is a 14 year old terrier mix.
The first day he was here, everything was ok. The dogs have all met before and they have gotten along in the past. However, trouble started last night when my husband came home from work. Our greyhound started baring her teeth and growling at the visiting dog. They were seperated before anything happened, but she has shown hostility since then.
Today, however, when I came home from work the same thing happened only this time she attacked him. (Luckily we got them apart before anyone got hurt). Does anyone have any suggestions as to what I can do to minimize this behavior? Obviously I am seperating them during mealtimes and keeping a close watch on them, but why does she show aggression when we get home?
Any helpf would be appreciated. Thanks!

Pembroke_Corgi

I think your greyhound is getting jealous and just warning the newcomer that DAD IS HERS! Same thing when you came home from work, I think she is just protective and wants all attention from you. I think it went well the first day because they thought it was just another visit... but when the pup didn't go home and stuck around, they're starting to think a new pup has moved in!!

You need to keep them separated as long as aggression exists and introduce them graudally more and more throughout the week. Do not leave them alone together unsupervised.

You just need to give your greyhound a little extra attenion, the poor girl probably thinks she's being replaced!! Who is the first dog you or your husband greeted when coming home from work?? Greet the greyhound and your corgi first, and your parent in law's pup last. :)

Be careful, that terrier is getting pretty old. Watch them very carefully, maybe seperate the two of them at night. Your dog might be protecting you, or, has others have said he may just be jealous. How long are you dogsitting for?

Thanks to both of you for the advice. We are dogsitting until Tuesday. I have been keeping them seperated or supervised and it seems to be going ok.
Luckily, the terrier is adjusting pretty well even though he is old. Even though there haven't been any other problems it will be nice to get back to normal when he goes back home!

Pembroke_Corgi