"środkowe" dziecko

She was also a middle child, though one of four.

Yes, I knew what was in store for me, the middle child, the one parents didn't care about.

Your middle child, however, has a less clear place in the family.

He was a middle child with an older brother and a baby sister.

At home, he felt no attention was paid to him, as a middle child.

He is the middle child from a family of seven children.

He was a middle child in a family of five.

She is the middle child of five in her family.

He was a middle child among the six children of his family.

He was the middle child of the five children in his family.