One of them checks the other's phone, gets caught, and instead of the usual fight about privacy, they end up on the couch until 2am dissecting why the urge to check was there in the first place. That is Scorpio and Scorpio. Nobody storms out over something like that, because they both already know the impulse from the inside.
Two fixed water signs together create a strange kind of relief. There is no need to translate feelings into smaller, safer language, no need to explain why a silence lasted three days or why a joke about an ex cut deeper than it should have. Both of them ruled by Pluto and Mars, both wired to want the whole truth of a person rather than the polite version, so the connection can go deep fast, sometimes uncomfortably fast, skipping the small talk stage entirely for something closer to interrogation. It can feel like finally being read correctly after a lifetime of being misread.
The trouble is that fixed plus fixed means neither one bends first. When a Scorpio couple hits a disagreement, especially anything touching trust or loyalty, both dig into their position and wait the other one out. Grudges can calcify instead of dissolving, because admitting fault feels like handing over a weapon. And since they share the same instinct to test loyalty before fully trusting it, they can end up running each other through the same suspicious paces over and over, each one hurt by a mistrust they would recognize instantly in themselves.
What saves this pairing is honesty used as a tool rather than a blade. When they choose to disarm instead of dig in, the loyalty between two Scorpios becomes close to unbreakable.