Derivation
<The variable parlink is created when co-parent data is processed before being appended to other spouse data:>
use ${newstata}\gen_identity_clean, clear
replace idmoth="" if idmoth=="UUUUUUU"
replace idfath="" if idfath=="UUUUUUU"
keep if idmoth~="" & idfath~=""
rename (idmoth idfath) (ident idspouse)
gen parlink=1
<After all data are combined parlink is used to id couples who remain in the dataset as they have lived together but have never reported each other as spouses:>
recode parlink .=0
bys wife husband: egen newparlink=min(parlink)