The family were attempting to come to terms with the upsetting news when medics noticed something else in the sonogram - the babies were holding hands.
Tiny Mason had his hand grasped tightly in his sister's.
The moving picture is a comfort to the baby's parents who may never get to meet him.
"Most twins when she's trying to take pictures and stuff they're kicking each other and hitting each other and she said without twins it seems like she was very protective over him," Ms McIntire said.
"I know I'm holding him, I'm carrying him but... she's the only one who can actually be there and is holding onto him... so it's comforting to know that if he does pass, he won't be alone."
Doctors told the couple that their son's only chance of survival would be to carry out heart surgery.
But they say they won't risk the surgery as the growing baby also had brain abnormalities, Ms McIntire said.
With medics unable to intervene to help Mason, Ms McIntire has a long and anxious wait before she will learn if she gets the chance to meet her son.
Both twins are due in September but the couple have been warned there is a likely possibility Mason could die in the womb before the date.
Mr McIntire said that whatever happened, the black and white sonogram would always be a special reminder of their babies.