Blood is thicker than water
A guest asked for a oneshot of Emma being in an accident and needing a blood transfusion. Neal is the one who has to give it to her and is scared but his parents comfort him.
"Are you sure it won't drain me of all my blood?" Neal whimpered. Snow reached out and stroked his forehead.
"Positive baby. The doctors wouldn't take away all of your blood. They just need enough to make sure Emma has enough too."
"And why does it have to be me again?" He asked. Charming sighed and squeezed his son's shoulder.
"It's hard to explain bud, but everyone has different blood types, and you can only have someone of your blood type give you blood otherwise it just makes you sicker. Your mom is A positive and I'm B negative. You and your sister are both O positive, but your blood is also a little different because of your magic. Because of that you are the only match that Emma has so they need to take some pal." Charming did his best to explain. Snow and Charming hated this. To solve one child's pain they had to give their other child some. It was a double edged sword. Neal nodded bravely.
"For Emma." He said, holding out his arm for the nurse who was ready and waiting. Snow and Charming smiled proudly at their brave little boy. Twelve years old and he was already braver than some adults.