The first time Anthea meets the younger Holmes brother, he's passed out in the basement of a drug den, seizing in agony, with a broken off needle from a syringe stuck in his arm.
She doesn't ask, but she'll sure as hell demand an explanation later. But she's been sent to collect him, and she doesn't like to disappoint.
Up until twenty minutes ago, she hadn't even known that Mycroft had any family. But when your almighty boss calls you, asking for a favor that's strictly 'off the record', it's not wise to refuse.
The picks the younger Holmes up gently in her arms (she's stronger than she looks), and carefully takes him up the stairs and out to the car. She lays him down on his side, and sits by his head, running her fingers through his dirty, mangled hair while he rambles deliriously about oysters and pence. He's a broken man, and if she had more time, maybe she could put him back together.
It occurs to her - as the younger Holmes lies there, gasping for air and trying not to choke on his own vomit - that the two brothers are very, very different people.
They drive to the hospital, and she take the younger Holmes inside, deposits him on a chair in the emergency room, and walks back to the car without another look.
The chauffeur drives her home, she pours herself a glass of wine (or five), and tries not to imagine what might be happening to the younger Holmes.
She doesn't ask. She really wants to know, but on the other hand, some secrets are best kept secret.