It was proven that Harry wasn't a great father. Hell, he was even aware that he wasn't a great friend. How many times had he forgotten about Neville's existence in school? Too many. However when he obsessed on something, he became hyperfocused. Draco? Check! Protecting people? Check! Making sure his kids didn't feel like shit? Check!
It was the only reason why he got up a little earlier than usual and had one of the house-elves track Jamie down. There was a slight downside at being here, with the no apparition, but he made his way to the tower with a plate containing a slice of cake and an unlit candle.
"Good morning," he said as he climbed the last step. "And happy birthday." He set the plate in front of Jamie and pointed his finger to light the candle. "It's not the surprise dinner everyone was planning, but you should celebrate your birthday, even if you do it in private as you prepare for another war. This is one thing I am qualified to talk about. Come on, make a wish and blow the candle."