His smile was huge as Sirius played along with his comment. Patting Sirius's knee, he offered, "You're my new favorite cousin. I hope you know that. And I have a lot of cousins to pick from." Even if it was technically a 'number removed' situation, it didn't really matter.
Teddy exhaled heavily, recalling that his time's Harry hadn't been too pleased with his decision but while Harry was his godfather, it was really Andromeda's opinion that mattered. And now Remus's who was offering his support without question. His huge smile turned to a softer fondness, leveled at his father. "I'd love to hear more about gran one of these days," he didn't have much knowledge about Remus's parents.
As for worst fears... He turned so he could lean his back up against Sirius so they were sort of 'side-by-side'. And then he ran his hands over his hair which then turned dark and long and everything else followed after. Two identical Sirius Blacks in one spot. Even the grins and the vibrating energy were the same.