Forever thinking about that Sarah Snook interview where she says “Shiv sees Tom as an extension of herself” and Tom’s chronic lack of an independent sense of self or identity. Shiv also struggles to maintain an independent sense of self and ultimately tries to define herself in opposition to her father and her family, especially politically, and she wants someone who will not challenge that sense of self or ask her to compromise in any way to accommodate them, because to do so would threaten the very shaky sense of self she’s constructed, which ultimately is too superficial to hold up in the face of such a request. Her sense of self is so wrapped up in independence and opposition that on some level the give-and-take of genuine relationships threatens it. (It’s also why we see her sense of self start to disintegrate when Logan offers her the CEO job and she has to start trying to rationalize her desire to be CEO with her sense of herself as someone fundamentally opposed to everything it stands for).
Meanwhile Tom’s absence of personal identity means he tries to define himself in relationship to other people. He wants to be needed because this gives him a sense of purpose. He wants someone he can mold his sense of identity around. He also tries to define himself through his working relationships and career ambition, but his consistent failure to effectively integrate into that group leaves him looking elsewhere for an anchor. His relationships with both Shiv and Greg began because they needed him, albeit in different ways and for different reasons. He defines himself through those relationships, particularly the idealized versions of them in his head - the idyllic romantic fantasy he wants with Shiv, and both the power trip and the friendship he wants with Greg - and real-world evidence which contradicts those fantasies shatters his own fragile sense of self. Whenever this happens he’s left attempting to “contextualize” it into a new sense of self, but the further reality moves from the fantasy the harder it becomes to do so, and the more disintegrated he begins to feel. When he ultimately sacrifices his marriage in 3.09 he needs Greg to come with him because he knows he’s about to lose Shiv, and he needs some kind of anchor, and Logan is too fickle a person to anchor an identity around (as his children have experienced). Greg is predictable and Tom understands the dynamic he has with Greg, so to bring Greg with him is to bring a sense of familiarity and stability as he upends the relationship that he has used as a defining part of his identity for so long.
(It’s also why Tom can’t leave Waystar; why he can’t go to the DOJ, and why he never considers the ‘third option’ of walking away, despite the fact that, as someone who is not a blood Roy, he’s maybe the only person who truly could. If he leaves Waystar entirely, then who is he? He doesn’t know. He has constructed his entire adult life around Waystar and the Roys, and to walk away would possibly be the single most destabilizing thing he could ever do)
