I had to purchase from Craigslist for the same reasons.

Yikes. I just checked Craigslist and it’s mostly filled with “looking for kitten” posts.

Odd Cat Sanctuary in Salem usually gets kittens a few times a year

If you don't mind the drive Sterling animal shelter has cats and kittens.

https://www.sterlingshelter.org/pet-finder/#action_0=pet&animalID_0=18764699&petIndex_0=1

Spent a few months looking from shelters and organizations looking for kittens. We got lucky on Craigslist. We got a healthy bonded pair of sisters.

Good luck. My wife and I got our old dog when we were in Alabama (shoutout to Greater Birmingham Humane Society). Things are really different up here. We ended up going with a (responsible) breeder for our current pair of cats because none of the rescues wanted to adopt to us with a little kid (aside—one of those kittens bonded almost immediately with the kid and the pair are now inseparable).

You also need to keep in mind that kittens are seasonal, even more so here than down South. You'll have a (comparatively) easier time finding one in late spring or summer than you will right now.

Yeah, I knew it wasn’t kitten season, but in the south there is just kittens all the time and then a hurricane of kittens in the spring lol

If you're on Instagram or Facebook there's a group down in St Croix called REAL Cruzan cats ( https://www.realcruzancats.org/) and they partner with shelters and fosters up here in MA and NH. They're getting into kitten season right now and have some gems posted on their social media already. I have two cats (3yo and 4yo Ms) from them and have helped with transports as well, the organization is pretty awesome and the cats are so stinking sweet. If you don't feel like you need to meet with your new kitten beforehand and are ok getting matched with an adorable island cat I highly recommend!

There's another island rescue called Island Paws Rescue ( http://www.islandpawsrescue.org/i-want-to-adopt.html) that works with Bahamian cats, but they don't have as easy a pipeline to get them north, better for Florida based folks. But another option i wanted to mention.

A pair of kittens is best for the kittens.

While I see the benefits, and agree that things like single kitten syndrome are a concern, I still don’t think it should be a requirement. There are ways to raise singletons of any animal; they just require extra attention.

The shelters I know will only adopt out a single kitten if another cat is in the house. Perhaps let them know you have dogs already? Maybe knowing other animals are there will make a difference.

This isn’t kitten season, so there will be fewer available. A young, adult cat is another option.

Besides the singleton issue, you may struggle to find a rescue that thinks it's a good idea to adopt out a cat in a 2bedroom with 2 adults, 2 dogs, and 2 kids. They'll probably wonder where the cat will be able to escape to if it doesn't want to be bothered by the dogs or vice versa.

I assume you own so asking your landlord for permission isn't a thing either.