Tennis Superstar Serena Williams has announced her engagement with Reddit Co - Founder Alexis Ohanian. Williams and Ohanian have been dating since 2015, but have kept their relationship quiet, with the exception of a few Instagram posts. Now, they have decided to open up about their relationship. Tennis star Williams has posted a photo of them at a costume party recently. Reports said that within minutes of the engagement announcement, comments started pouring in on the photo and were dominated with congratulatory messages and emojis.