the_debt_of_time

"Dorea was brilliant. Cunning and ambitious, but the most loving and accepting
woman I'd ever met," Sirius went on. "She didn't just take me into her home when I ran
away. I'd practically been living with your dad and his family from the start of Hogwarts. I
think I started calling them Mum and Dad when I was fourteen or fifteen. They took in
Remus, too. Remus had a rough go of it with his family as well, but the Potters, Dorea
especially, we were hers. When she died, she was surrounded by her children, even though
she'd only ever given birth to James."
Harry took the book into his lap, flipping through the pages of the Black Family
Tree, which Sirius knew could be difficult to decipher, considering half of the Wizarding
world was interwoven into the family in one way or another.
Sirius laughed to himself as he noted that Harry had purposely skipped over the
page showing the Weasley connection to the Black family, clearly not too keen to find out
just how closely related he and Ginny were.
"There she is." Sirius pointed to Dorea's name, letting Harry make the connection
himself.
Harry scanned the family tree, his lips quirking up when his fingers brushed over
his parents' names and then to his own. He lingered over the date of their deaths for a
moment before his brow furrowed. Sirius knew exactly what had drawn his attention: the
only movement on the page was a name down and to the right of James's, fading in and
out.
"Who is Mia Potter?"
Sirius anxiously chewed on his thumbnail while bouncing his leg beneath the table.
Instead of answering Harry's question, he reached for the tumbler of firewhisky and took
a long drink, savouring the flavour which gave him a boost of courage—not from the
alcohol but from the memories it contained.
"Mia Potter... was your father's sister."
Harry's jaw dropped. "My dad had a sister?"
Sirius dipped his head.
"How come I've never met her? Is she still alive? Why didn't anyone tell me about
her?" The questions came quickly, not giving Sirius a chance to answer even one until he
reached out and put a hand on Harry's arm to draw his attention.