Part the first, observed and written to the peregrine forum this afternoon:

So Kekoa's been dozing on the louver, minding his own business in the
shade for over an hour, when Maya suddenly flies in right next to him.
She bumps into him. He goes HEY! and steps away a step. She wants
attention. She steps on the tip of his wing and combs it with her foot.

HEY!

He scuttles a little further away from her, and she starts grooming
herself.

Right, Sis. You preen your own feathers, y'hear?

And then Kekoa starts grooming too, each being the mirror for the other.

Later on tonight, they were back on the louver after (I assume) dinner off somewhere; Kekoa got there first and hopped up onto the ledge just above Maya when she came in. He likes that window seat; let his sister have the emergency exit row.

They were together a goodly while with me thinking how sweet it was that those two young fledglings liked to be side-by-side still–when all the sudden they started acting like siblings anywhere. Teasing. Protesting.

Hey! Kekoa has the good seat! I want it!

Maya reached slightly up and started pulling on his wing.

Hey! Mom said we should beak kind to each other!

So I’m kind-of-beaking you here, you got a problem with that?

Little Kekoa gathered his wings together and flipped his tail a bit out of her way. She moved over and leaned, twisting her head in from underneath it as if she could get away with it that way, and ran her beak again down the tip of his wing, grabbing a goodly chunk of feather in the process: Hey, bro! Here, you spilled some anchovies off that pizza, let me help you clean it up.

Get OFF! He danced away, turning around in his spot, still carefully keeping that upper corner.

This went on four times, and in between, Maya was reaching under the ledge, grabbing something unseen and twisting, as if she could undo a screw and turn the whole scene into a Wile E. Coyote moment.

Kekoa simply tucked his tail and his wings out of her way and got them again out of her reach. But he stayed in that corner. That was his spot and he wasn’t going to budge.

Small and nimble beats big and slow any day. So there, Sis.

Notice that, two hours later, they are still in the same places. There’s the whole rest of the window ledge if Maya wants up, but she has stayed standing looking at him. Standing sentry in the night like her mother did.

And he in return watches over her, over his shoulder.

No other bird could possibly do for company at this stage in their lives.