midparent
/ˈmɪdˌpærənt/Definitions
1. noun
Either of the two parents of a child in a family
“The midparents of the couple had a close relationship with their grandchildren.”
2. noun
An average of the heights or other measurements of the two parents of a child, used in estimating the height or other characteristics of the child
“The midparent height was used to estimate the child’s expected height at adulthood.”