The scene in Baker Street where Mrs Hudson, while fussing over her “boys” and serving up breakfast, scolds Mycroft about deliberately sending his little brother into danger, because “family is all we really have in the end.” Mycroft tells her to shut up, and Sherlock and John immediately jump down his throat about it, taking him aback for a few awkward seconds. The dialogue, Mrs Hudson’s point and the visual composition of the scene make it pretty clear- Mrs Hudson, Sherlock and John actually function better as a family than their ‘real’ family do. Keeping in mind Sherlock and John have rocky relationships with their siblings, no parents mentioned, and Mrs Hudson is a widow who apparently has no biological children of her own. Sherlock and John eating breakfast in their pyjamas while Mrs Hudson clucks over them form a sharp contrast with Mycroft, standing a few paces away, stiffly dressed in a suit and looking totally out of place.

SOURCE - TV TROPES