Regulus Secret

(Voldemort was defeated. Lilly eloped with snape.- will not be in the story but probably be mentioned.)

James and Regulus broke up when Regulus found out Lilly was in labor with James child. Regulus was heartbroken, sad, but mostly pissed since he found out he was pregnant with his child too. When Regulus tried telling James, he would ignore him. Regulus hated him for that, and when he was making a plan to kill himself, he stopped when a Barty crouch jr caught him.
Barty told him that if he did this, he would kill two lives.
He and Barty where even closer than before and soon they started dating.
Regulus never harmed himself and became head of the Blacks since sirus was disowned.

Regulus kept thinking, "What would happen when the baby's born. Walburga would definitely corrupt it." Luckily, fate was on his side,
Walburga died as well as orion, of dragon pox

So Regulus married his loved one, Barty, and then Stolas Black was born.

Years later,
After Stolas turned 1 year old, Regulus gave birth to another child, Octavia. But even when Octavia was born, Barty nor Regulus played favorites.
When Octavia was 5 year old, Barty died.
Regulus was devastated, and so was Stolas but couldn't show it as Regulus was now the head of both houses of black and crouch.
When Stolas turned 11, he got his hogwarts letter as well as 10 year old Octavia since she was an early acceptance.
They all went to diangon Alley, and they went to the quiditch shop where they met backstabber's sirus black and james Potter

James was shocked to see regulus black his ex lover,
James was also surprised to see a wedding ring on Regulus hand.

and sirus was crying to see his little brother whom he had not spoken to for 20 years.

Regulus was not expecting to see them but was calm since both his kids were there.

what would happen when both sirus and james see two kids that were a spitting image of Regulus expept for the hair and eyes.

How would the kids react?