When can I introduce two kitten litters to each other?

Hello everyone, so glad a found this forum, I have a problem that I can't seem to find an answer to.

    The situation is this: My daughter's cat, Lulu slipped out shortly after moving to our new home. I know bad pet owner, she was pretty young and with move we just kept putting it off. She gave birth about 5 weeks ago to healthy litter of 4, we knew she was due anytime but what a surprise! She didn't make a peep, my daughter woke up to Lulu sitting on her like every morning, except she kept running off to the corner of the room and there they were with a happy Lulu just beaming over them.

    Four days later we are sitting in the living room when we hear a cat moaning like it is just being torn apart, we go out and find the little black stray the kids had taken a liking to outside giving birth in driveway! She was so distressed dragging the half born kittens all over the gravel and just miserable. We had to help her, so we we got a box and some blankets and gathered her and the lil ones up and brought her in. She had 4 living kittens and one stillborn.

    Things looked wonderful for the first few days Lulu was attentive and any momma could be, and the new cat was bit less so, she took great care of the babies, but was also very interested in her new surroundings. But then the unthinkable happened one of the new cat's kittens vanished. We had no idea how, maybe my cat was jealous and took off with it, she is spayed and never even seen a kitten before, or maybe my husbands pug, or maybe the momma just ate it? We just didn't know. To be safe we sepperated the litters completely and everything seemed fine for two more weeks, when this time one of Lulu's kittens vanished. There was no mystery this time though, we found the poor little guy under our bed, where the pug hid his toys. We buried the little guy with still born and locked down the kitten room. The older litter has the run of the floor and the younger has a play pen. But all of them are getting very active and the pen will not hold them much longer, so is it okay to turn them all lose in the room? Well the mother cats be able to tell whose is whose? I don't know much of anything about the new cat aside from what I have seen the last few weeks, but should I worry about health risks letting these little guys mingle?  My house is small and I don't really have another space that I can keep these little guys safe so I really need to know if they can be free to roam with each other or if I need to find a new home for the younger group? Oh and they are right around 4-5 weeks old now.

Thanks so much for reading this, I am so sorry to be so long winded.

In terms of getting along the two litters should be fine. Kittens are very adaptable in that way. The Mom's will know which kittens are theirs, though it's not uncommon for Queens to nurse each other's kittens. 

How much contact have the Moms had with each other? That is certainly a bigger concern as one may be territorial and they may fight. So, if they haven't met, start by doing that slowly (and if this is the case say so and I or someone else can elaborate). 

The other big concern is cross contamination. Meaning, if one litter has an illness and then exposes the others to it. But, from your description of the set up there has already been a fair amount of cross contact so I don't know that at this point it matters. Plus, if they were sick they would have likely showed symptoms by now. 

The biggest concern of all however is keeping them separated from the pug! I'm assuming he was also responsible for the first kittens death since he did it to the second kitten and you just can't let it happen again. So, you need to find a way to keep him confined from the group. That is a lot easier as you may just be able to gate him off to one section of the house. I'm sure with a little creativity you will think of something!

Have you contacted any local shelters about your situation? If not, it may be worth doing so. Many shelters will allow you to "foster" both sets of kittens. You would likely be responsible for all their basic care costs but they will take care of any and all vet costs and will find them good homes. It's a great way to ensure that they are properly dewormed, vaccinated, and altered without breaking the bank. And, you get the benefit of their scrupulous screening process in finding proper homes. Otherwise, talk to your vet about a possible group discount as these guys are almost to the age where they need to get started on their de-wormings and vaccinations. 

Finally, remember that both Queens can come back into heat at anytime so make sure they stay indoors and away from any intact males until after they are spayed so that this doesn't happen again to either of them! 

Continue to ask questions if you have them. Welcome to TCS. 

    Wow thanks for the quick response! The Queens seem to get along fairly well. So far neither has interfered with the other's litter, but when a kitten is upset it is not uncommon for the other Mom to come take a look. And yes the kittens do share a room right now, and the pug is locked out of it. He had previously been fine around kittens and puppies, but just goes to show never take a risk like that.   

    I had no idea that some shelters offered things like that and that sounds wonderful! I will absolutely look into it. We have three of them marked for good families right now. But I was really worried about finding a good home for the rest. We were pretty much at our limit with the two cats and one pug,  

   Keeping two Queens inside has been no problem, Lulu won't leave her babies for much more than an hour, and Alex is too taken with having a home to even remember outside exists. Thanks again for the welcome and answers.
 

Happy to help. Since the girls get along fine and there has already been intermingling I see no problem with letting them all out together. Just keep a close eye the first day or so to make sure nothing dramatic happens. 

It's great to hear they are both such attentive mothers that they are showing very little interest in anything else. I certainly don't want to beat the subject to death but I will add that once they go back into heat there is very little they won't do to get outside and find a suitor. You know that firsthand considering that's what your resident girl did! All I'm saying is that even though they seem content now don't drop your guard for even a second when it comes to that. If one wants out and you are not exceptionally careful the little Houdini's will find a way. Same as you clearly can't trust your Pug around kittens, don't trust these girls around outside doors! 

Best of luck in finding a shelter to work with- it helps them as they can add to their numbers on paper without adding to their numbers in the shelter. And, they will keep the adoption fee which is a huge help in furthering their mission (and still won't be a quarter of what you would spend on vet care out of pocket). Even though you have good families lined up for three I would still encourage you to have them go through the shelter process same as anyone else would have to. Sometimes our best friends and family members don't make the best pet owners. And, it will be easier for you all around versus having the shelter treating some of the kittens while you are responsible for the others. Any good future family will have no problem filling out some paperwork and paying an adoption fee that covers the most basic vet costs that is still way less than what they would pay having to do it on their own. Start with the no-kills and rescues as they are more likely to have these sorts of programs in place. Just get online and see what you can come up with!