You can join online forums where your target audience hangs out, join in the conversations and become a liked member, and mention your websites where helpful and appropriate. This takes time to build up though.
You can also try getting picked up with someone big on social media who has a similar audience by following them, commenting, sharing their content, emailing them to tell them how much you appreciate their work, and then once you build a connection, introducing them to your websites which they might feature.
You can also try a promotion exchange – connect with similar websites where the people you want to come to your website are looking, and do a blog tour.