An only child is a person who does not have any siblings, neither biological nor adopted.

Mattia has another biological sibling, Paolo's first son Davide.

Bogaert (2006) replicated the fraternal birth order effect on male sexual orientation, in a sample including both biological siblings and adopted siblings.

In this incarnation Liz is Hispanic and she and Mark are biological siblings.

Also, biological siblings are more similar in personality than adoptive siblings.

She learned at the age of 8 years that she had a biological sibling; however, their contact throughout childhood was limited.

What is the known medical condition of any full or half biological siblings?

So the Liebls' son Matthew has two biological siblings being raised by a black family in a nearby suburb.

They went out to dinner at an Italian restaurant on Long Island with his biological siblings, Christopher and Jennifer.

The advantage of having subsequent children by the same donor is that these will be full biological siblings, having the same biological father and mother.