Just to make this more understandable.

In this bellatrix is not Matteo's mother - it was a pure blood named Sofia, who voldermort killed when she tried escaping with Matteo when he was a child.

Cassiopeia (Cassie) Lily McKinnon - daughter of  Marlene McKinnon and ex daughter of Sirius Black (you'll see why). Wife of Matteo Riddle, they got married a few years after the war and had baby girl who they name Sofia Marley Riddle.

Sofia Marley Riddle:
Picture yourself or whoever you want.
Brown hair - grey eyes.
Age: 16
Mother: Cassie Mckinnon
Father: Matteo Riddle
Siblings: None yet, Cassie is about 8 months pregnant with a boy.

James Sirius Potter:
Played by Timothee Chalamet.

Age:16
Mother: Ginny Potter (née Weasley)
Father: Harry Potter
Siblings: Albus Severus Potter, Lily Luna Potter.