IPUMS family interrelationship variable SPLOC provides the person number (PERNUM) of the respondent’s spouse based on an IPUMS algorithm which incorporates responses to RELATE, SEX, AGE, and occasionally order information. You can find more details on how spouses are matched on the SPRULE variable description tab. SPLOC includes both married and cohabiting same-sex couples. It does not require either individual to be the householder. You can differentiate between married spouses and cohabiting partners with MARST and specifically identify same-sex couples by attaching SEX in the attach characteristics option in the extract request menu. If you’re looking for the original self-reported responses, you can find them in the variables ASPOUSE and PECOHAB.
I hope that helps!