Founder's spouse working at a startup?

I've come across two early-stage venture-funded startups recently where a founder's wife has a "Head of X", but non-founder, role. In both cases they have the right background and seem to do good work, but it still strikes me as an odd decision - lots of possibility for things to go wrong, conflicts of interest real or perceived, etc.

Have any of you come across this before? Is it common? In your experience, has it ended badly? Do you consider it a red flag when looking for jobs?