Oh man, I've been obsessed with 'Moriarty the Patriot' since I started it, and Albert is honestly such a foundational yet weirdly quiet piece of the whole puzzle. He's the eldest of the Moriarty brothers, but he wasn't born into the family—he was an orphan they adopted after the whole tragic fire that killed William and Louis's biological parents. So right off the bat, you've got this interesting dynamic where he's both integral and slightly separate. He becomes the 'public' Moriarty, the one who inherits the title and the estate, which provides the perfect cover for William's schemes. Without Albert holding down the fort in high society, playing the respectable aristocrat, William couldn't operate from the shadows nearly as effectively.
A lot of people just see him as the supportive older brother, and he is, but he's also way more complicit than that. He's fully aware of and agrees with William's goal of tearing down the corrupt class system, even if his methods are more about maintaining the facade. He uses his position and influence to gather information, secure resources, and basically run interference. There's a steel to him beneath that polite exterior; he's made his peace with being part of a revolution that might require terrible things. I think his relationship with William is less about blind loyalty and more about a shared, deeply held conviction—they're partners in this, even if their roles are totally different.
Sometimes I wonder if he feels the weight of it more, being the one who has to look other nobles in the eye while knowing the plan. That scene where he's interacting with Sherlock at a party, all charm and grace, while mentally they're all circling each other... it's such good tension. He's the anchor that lets the other two fly, but anchors aren't passive; they grip the seabed with everything they've got.