Find Mercurial Changes Where Both Parents Are In The Same Named Branch -

i'd list changes in mercurial repo merges both parents in same named branch change itself.

i.e., merges not 1 named branch another.

i know how list merges:

hg log -r "merge()" 

but i'm having trouble figuring out how express "both parents in same named branch change itself".

this best i've come far, works if can specify branch name (default in example below).

it doesn't seem include changes shouldn't, can't it's not excluding changes shouldn't.

hg log -r "children(p2(branch(default)) & branch(default)) & branch(default) & merge()" 

any feedback or better answers welcome!