The first thing Ethan Carter noticed was that his newborn twins looked nothing alike.

The first baby, a boy, arrived at 4:17 in the morning with a furious cry and a head of dark brown hair. He had Hannah’s small chin and the same deep crease between his eyebrows that Ethan had seen in every photograph of himself as a baby.

“Hello, Noah,” Ethan whispered as the nurse placed the child against Hannah’s chest.

Hannah laughed through her tears. After three years of fertility appointments, one miscarriage, and months of being afraid to celebrate the pregnancy, their son was finally here.

Six minutes later, the second baby was born.

She was smaller than her brother, with pale blond fuzz covering her head and gray-blue eyes that opened almost immediately. She did not scream the way Noah had. She released one soft, offended sound and stared up at the delivery-room lights.

“Lily,” Hannah breathed.

Ethan touched the baby’s tiny hand.

“She looks nothing like him.”

Dr. Leah Monroe glanced up from the end of the bed.

“They’re fraternal twins. They can look as different as any other brother and sister.”

Ethan smiled, embarrassed by his own comment.

“I know. I just expected them to look like twins.”

“They shared a womb,” Dr. Monroe said. “Not a face.”

For the first several hours, nobody treated the twins’ differences as anything unusual.

Noah had Hannah’s darker coloring. Lily was fairer. Noah weighed almost a pound more. Lily had a narrow nose and a faint dimple in her left cheek that neither Hannah nor Ethan recognized.

Family photographs were taken. Ethan called both sets of grandparents. Hannah lay exhausted in bed with one baby tucked against each side of her.

For a few precious hours, nothing existed outside that room.

Then Lily became jaundiced.

It was not severe enough to cause panic, but the yellow tint in her skin appeared earlier than the nurses expected. Blood was drawn to check her bilirubin level and determine whether there was an incompatibility between her blood and Hannah’s.

At eleven that morning, a laboratory technician called the maternity floor.

Dr. Monroe read the results twice.

Hannah was type O positive.

Ethan’s medical chart, completed during the pregnancy, listed him as AB positive.

Noah was type B positive, which was completely possible.

Lily was type O positive.

Dr. Monroe stared at the page.

A mother with type O blood could pass only an O allele to her child. A father with type AB blood could pass an A or a B allele—but not O.

An O-positive child could not be biologically produced by an O-positive mother and an AB-positive father.

Unless one of the records was wrong.

Dr. Monroe ordered the tests repeated without telling the parents why.

The second results were identical.

She then asked a nurse to draw new samples directly from Hannah and Ethan rather than relying on their previous medical records.

Ethan joked while the nurse tied a band around his arm.

“Do I at least get a cookie for this?”

The nurse forced a smile.

Hannah watched her.

“What aren’t you telling us?”

“It may be a laboratory issue,” the nurse said. “Dr. Monroe will speak with you when she has complete information.”

Hannah looked toward the two bassinets.

“Is something wrong with Lily?”

“Her bilirubin is elevated, but we’re treating it. She’s stable.”

“That isn’t what I asked.”

The nurse hesitated.

“I don’t have enough information to answer yet.”

When Dr. Monroe returned that afternoon, she closed the door behind her.

Ethan was standing beside Noah’s bassinet, trying to wrap him in a blanket. Hannah was holding Lily under the blue phototherapy light, shielding the baby’s eyes with one hand.

Dr. Monroe pulled a chair closer to the bed.

“I want to start by saying that both babies are medically stable.”

Hannah immediately tightened her arms around Lily.

“What happened?”

“We found an unexpected blood-type result.”

Ethan gave a short laugh.

“That sounds less frightening than the way everyone’s acting.”

“It may still be a testing or documentation error,” Dr. Monroe said. “But we repeated the samples. Mrs. Carter is O positive. You are AB positive. Noah is B positive.”

“And Lily?”

“O positive.”

Ethan waited.

When Dr. Monroe did not continue, his expression changed.

“What does that mean?”

“It means Lily’s blood type is not an expected biological combination from the two of you.”

Silence filled the room.

Hannah looked from the doctor to her husband.

“I don’t understand.”

“Blood typing cannot establish paternity,” Dr. Monroe said carefully. “It can only rule out certain possibilities. There are rare laboratory and genetic circumstances we would need to consider. We should not make assumptions based on this alone.”

Ethan’s voice became quieter.

“But normally?”

“Normally, a man with AB blood would not father a child with type O blood.”

Hannah’s face went white.

“No.”

Ethan turned toward her.

She shook her head before he said anything.

“No. Ethan, no.”

“I didn’t ask you anything.”

“You’re looking at me like—”

“I said I didn’t ask.”

Dr. Monroe stood.

“I recommend repeating the blood analysis through an independent laboratory. If you both consent, we can also arrange DNA testing. That will give us a clear answer.”

Hannah stared at Lily.

The baby slept beneath the blue light, her tiny chest rising and falling, unaware that three adults were suddenly afraid of her blood.

“This has to be a mistake,” Hannah whispered.