In outliner you can use ctrl + left click to select both parent and children, but in 3d view there is no selection option that also include the parents i.e when using shift + G, while Shift + ] also include the parent sadly if there are 2 parenting object the children of the secondary parent again are not selected
TL;DR : it would be nice if you can do what you can do with outliner group selection when using Shift + G
thank you have a nice day, i love you all