Hi Flossie,
It's impossible to say for sure without logging into the sites and checking for active profiles.
If he was on them in the past (and even if he wasn't), dating web site promotional/spam emails are a common type of spam.
Also, it's typical for a parent company to own several dating sites, so it's also possible he was on a site and that parent company is sharing his data between the marketing teams and that's why additional sites are sending him emails now too.