It was easy, with Keith. Maybe not at first, but eventually it got there. It was comfortable, the way they fought. It was a dance they choreographed together, familiar in the soft edged jabs and names they'd throw each other's way.
At first, of course, the fighting was messier and less choreographed. Lance would be the first to admit that it was genuine back then. But somewhere along the line, Keith became more than the mullet that was somehow always three steps ahead of him seemingly without trying; he was a teammate. A friend, believe it or not.
(Lance hadn't believed it at first. Hunk had straightened that one out with him in a private “Best Friend Feelings Jam”. Though he was loathe to admit it at the time, Hunk broke his stubbornness. He always did.)
And somehow, without discussing it, they traded steps and found something reliable in the mess they found themselves in. Having something that was Known helped. It was comforting.
Then, when Shiro disappeared, things changed.
There were times when Lance would throw out a line and Keith would respond in kind, like usual. Other times, Keith would stay quiet or his face would twist in an almost imperceptible way. At those times, Lance would have feel a strange twinge in his heart, familiar by itself, but new with Keith.
Lance, at his core, was fiercely protective of his loved ones. He needed to make sure his people were doing fine. Keith was not fine. So, he changed the dance.
The times Keith wouldn't rise to his invitation, Lance would let his persona rest for a second and would reach out to him, barbs tucked away. It was only in his absence that Lance realized just how much Shiro had done for Keith. The times Shiro would have stepped in to reassure or reprimand Keith now hung heavy in the room as no one stepped forward to take his place. Coran kept a calculated distance with all of them, kind but an observer. Allura already had assumed the weight of the universe on her shoulders, helping Keith required emotional work that she didn't have in her. Hunk and Pidge were well meaning, but both were easily overwhelmed and honestly weren't totally sure how to help Keith. Not that Lance did, really. No one could replace Shiro. (Family could never be replaced. Even if Lance truly considered the other members of Team Voltron his family now, it didn't replace his family back home. It just made his family a little bigger.)
Shiro's absence was never bigger and more suffocating than when Keith stepped out of the Black Lion, miserable to his core that it had chosen him. Lance thought about how this would all feel for him, how difficult it must be to keep going, as the silence stretched out. It was unbearable. Keith was hurting, he needed someone. So he stepped forward, crossing through the silence and deliberately bypassing the steps and twirls the two of them had gotten so used to, and put his hand on Keith's shoulder, and did his best to prop Keith back up.
It was new, and it wasn't nearly enough, but it was something.
It was a start.