Looks like a lot of peat in that mix. How much light do they get?

I have them in a west-facing window. It's not direct sunlight in here, but it's pretty decently lit, I believe? I keep them by the window pretty much all day. The soil is a 'Miracle-Gro: Cactus, Palm & Citrus' potting mix. Does it not appear like a good mix for the plant?

I've had these for about 2-3 years, closer to 3. These were actually gifted to me, each individual stalk, about 1 year apart. They came from a larger jade, which was probably older than this. At one point, I only had one of these jades in this pot, but after receiving the 2nd I decided to put them together. I'm still not 100% sure if that was the right move, but I guess they're doing okay, huh? I will have to pick up a bag of perlite. I'm not completely sure if Home Depot will have crushed sand/granite, but I'll keep an eye out. Can crushed granite be added to any type of plant, like both cacti and regular houseplants? What benefit does granite and sand add to mixes?

The coarse sand is just for drainage. The key is it must be coarse (not fine) and not contain salts. Perlite serves the same purpose and might be easier to find and work with. Here is a big jade at my office that is outside for the summer.

Wow!!!! That is gorgeous. My dream is to have a jade like that someday! I know they're fairly slow growers, though. Any tips for optimal growing of one? I will definitely pick up some perlite and see about the sand and gravel. Potentially, could one of the two stalks I have grow into something like that? Would I need to separate these two at some point, or can they remain together?

Just a tip, if you get perlite be sure to sift out the small bits and dust with a kitchen sieve (and wear a dust mask). Those small particles reduce the aeration of your soil mix, which results in reduced root health.

Similarly, if you get sand ensure it is very coarse sand. If it is something fine like play sand, it results in higher soil compaction over time and similarly an unhealthy root zone.

You could say that sand particles drain well, but they also hold a surprising amount of water through cohesion (in between all the small particles). So fast draining is not really the same as having low water retention.

If your plan is to keep this purely indoors at your window, a much higher percentage of perlite may be beneficial - perhaps upwards of 70%.

Crushed granite or granite grit is an excellent addition to soil mixes. I prefer it to perlite most of the time. The most common type used for plants is called chicken or poultry grit (grower size) and it is very cheap and comes in different sized bags. Farmers use it to help chickens grind up their food in their gizzards.

A good goal in creating an indoor soil mix is low water retention because light levels and temperatures are typically lower and a high level of aeration to give oxygen to the roots. =)