I don’t think Ethan and Mia would be bad parents but they do not give off the vibe they want(ed) kids? Like even before encountering hell child Eveline, they’re both 30+, been together for like 4 years, and after the Dulvey Incident it really makes no sense imo. Mia also says:
Like ok I’ve deduced that they probably fucked like crazy while back together bc Ethan initiated it for the first time in their relationship and that was just too GOOD SHIT™ to pass up on