Robert Grodt was a volunteer medic at the Occupy Wall Street protests in 2011, when he pulled Kaylee Dedrick, who had just been pepper-sprayed in the face, out of the crowd to treat her.

The pair quickly hit it off, and when video of Ms. Dedrick being sprayed in the face captured the world’s attention, the spotlight turned to their budding romance. They again garnered media attention the next year, when they had a daughter — quickly nicknamed “Occubaby” — because she was conceived in the protest camp in Manhattan’s Zuccotti Park where the pair had been camped out.

But then he made a dangerous decision that few young Westerners have made — joining a Kurdish militia fighting in the Syrian War.