Paired Units

Technical Definition

"Paired Units" are a group of two or more robots who are made to work very closely together. It's also the term used to describe the relationship between such robots, i.e. "they are paired units"; "he is their paired unit".

To this end, each is typically coded to think of their paired units as if they were altogether one larger unit with independent moving parts. This extends to their self-preservation directive being hard-coded to include their paired units. They may typically be addressed as if they were one unit, too, especially if they're intelligent enough to delegate sub-tasks between themselves.
This could be loosely compared to the experience of systems; having one larger, shared identity along with their individual identities.

Paired units typically have the same primary directive, though some may be specialised to complete one specific sub-task of their shared goal. For example, if they're made to assemble something, one may be built strong enough to lift the parts while the other has the tools to secure the parts in place.

The two most prominent examples of paired units in Sonic canon are Dekkoe and Bokkoe, appearing only in Sonic X; and Orbot and Cubot, first appearing in Sonic Colors and still appearing in new releases.
Scratch and Grounder, while working together often and being part of a larger squad, were not paired units in the technical sense. This is why they were so competitive among themselves, and why they were deactivated. Paired units see goals as shared, and would not purposely sabotage each other.

Lived Experience

The experience of being a paired unit can be hard to explain. Your lives are closely entangled, for better or worse, for as long as you run. You've known each other for as long as you've each existed. Everything you have in common becomes part of your shared identity, and every difference defines your individual identities.

Having an identity defined by its contrast with someone else's means, without them, the individual identity feels as if it falls apart. You can't really be "the Serious One" when you're the only one. Somehow, in their absence, all you have left is the identity you shared with them.
That very much extends to how people see you, too; if you're separated, people find it weird, and wonder where the rest are. All they can focus on is that your paired units are missing; your individual identity gets glossed over. It's only when you're together that your individual identities can be seen.

The fact that your self-preservation directive includes your paired units leads to a feeling similar to a phantom limb impression of their body. Unlike normal empathy, where pain will be felt in the same place on your own body, paired unit empathy is felt there instead. Being separated from your paired units and/or being unsure of their condition can create a static feeling like a limb being unresponsive/'falling asleep'. If they're separated long enough, it can start to feel like a dull ache. Believing they've been permanently destroyed in some way is sharp and crushing. It feels as if something vital has been ripped away and destroyed.