Harry Potter was now a grown man no longer a child, this meant he wasn't as naïve as he was before, he didn't have the childhood innocence anymore, if he ever had it to begin with. He was groomed into a saviour and that's what he was, tho he wasn't groomed into saving himself, this realization led him to belive he couldn't mourn Sirius the way he did before.
When he was 15 he thought he could have killed himself when Bellatrix murdered him, he still loved Sirius of course, not in a way that a godson should think about his dead godfather.
Now when Teddy was 15 he felt quite disgusted at the thought of Sirius wanting him, but it was somehow different wasn't it? No it couldn't be, he felt hopeless and empty, even emptier when he realize Sirius filled him at the age of 15.
On some nights he thought he could still feel Sirius pumping into him, he shoved his head in the mattress like he did before, but now there was nobody behind him. He gritted his teeth as a tear slid down his face, everytime he looked into the night sky he could see Sirius, his brightest star, he was so perfect but you know whats another word that starts with p? its pedophile and that is what he was, the realazation shattered him, and he couldn't be rebuilt because the only one who could tape him back together was the one who broke him, he would still think about him, but no longer shared stories, ashamed and scared Teddy or anyone could figure out how Sirius defiled him.