Following is a response from DHS staff member, Tom Pullum:
You just need to merge the mothers in the KR file with the women in the PR file. This could be a "m:1" merge or you can use an older version of the merge command, which I prefer. The following Stata code shows how to do it, and shows that the mother's PR data is repeated for each child.
cd e:\DHS\scratch
use "C:\Users\26216\ICF\Analysis - Shared Resources\Data\DHSdata\ETPR81FL.DTA", clear
keep if hv117==1
gen cluster=hv001
gen hh=hv002
gen mo_line=hvidx
sort cluster hh mo_line
save ETPR81temp.dta, replace
use "C:\Users\26216\ICF\Analysis - Shared Resources\Data\DHSdata\ETKR81FL.DTA", clear
gen cluster=v001
gen hh=v002
gen mo_line=v003
sort cluster hh mo_line
merge cluster hh mo_line using ETPR81temp.dta
tab _merge
keep if _merge==3
save ETKRPR81FL.dta, replace
gen children_per_mother=1
collapse(sum) children_per_mother, by(cluster hh mo_line)
tab children