A couple in the US is rearing the rarest type of twins in the world - they have different fathers.

Like most twins, 11-month-old Justin and Jordan have a lot in common.

However they have different biological fathers and are half-brothers.

Their mother, Mia Washington, had an affair that resulted in two babies, born at the same time, but fathered by two different men.

The parents went to a DNA Lab in Texas after noticing the twins have different faces.

Paternity tests revealed there is a 99.9% chance that Justin and Jordan have different fathers.

Doctors call twins that have two different fathers heteropaternal super fecundation. There are only a handful of documented cases in the world and medical experts say the boys are a miracle of science.

Laboratory officials said they have never seen this type of result, nor do they expect to see it again.

The condition occurs when a woman releases multiple eggs during ovulation. If the woman has more than one sexual partner within the same time period, sperm cells can fertilise two separate eggs.

The biological father of one of the twins said he has forgiven his fiancée's infidelity.

He has vowed to stay with her and raise both boys as his own.

Ms Washington says she takes full responsibility for her actions and plans to tell the boys about their DNA differences when they are old enough to understand, but has no plans to tell the other father.