Neither one has male anatomy so wondering if they are litter mates that were dumped and stayed together. Just seems odd these two would hang out so much together. I titled this Best Friends Forever.
So, if these two are females, and haven’t been spayed, you may find yourself with a whole bunch of kittens in the near future. You should try to get them in for a spay ASAP, even if you need to cat trap them to do it.