A peak's

Summit (topography)

In topography, a summit is a point on a surface that is higher in elevation than all points immediately adjacent to it. Mathematically, a summit is a local maximum in elevation...

 line parent is the closest higher peak on the highest ridge leading away from the peak's "key col". A col is the lowest point on the ridge between two summits and is synonymous with pass

Mountain pass

A mountain pass is a route through a mountain range or over a ridge. If following the lowest possible route, a pass is locally the highest point on that route...

, gap, saddle and notch. A peak's "key col" is the lowest point on the ridge which connects the peak and a higher peak. If there is more than one ridge which can be followed to a higher peak then the line parent is the peak closest to the key col. Usually, a line parent must meet some prominence

Topographic prominence

In topography, prominence, also known as autonomous height, relative height, shoulder drop , or prime factor , categorizes the height of the mountain's or hill's summit by the elevation between it and the lowest contour line encircling it and no higher summit...

 criteria, which might vary depending the author and the location of the peak.

There are at least two other kinds of peak parentage. Island parentage, which is also referred to as encirclement or topographic parentage; and source parentage.