My 27 year old ex boyfriend is in a relationship with an 18 year old boy... How do I deal with this shocking news?

My ex boyfriend (3 year relationship, broke up with me 6 weeks ago due to him feeling neglected due to my depression and OCD) told me this week that he is now in a relationship with an 18 year old boy… My ex and I are both 27…....

One week after our break up my ex met him for the first time to hang out… That’s when he ‘fell’ for him…

My ex and I met this boy on an MMO one year ago. We knew the boy was gay and both got on with him a lot but he was very clingy with my ex (always messaging him every single day). I didn’t care about how close they were. I never thought in a million years he would be a threat to our relationship because my ex was straight (only ever had female partners – 3 before me). I never thought he’d look at an 18 year old in that way either if he was a female.

My ex is feeling very confused and it has been difficult for him to come to terms with apparently.

How do I deal with this shocking news?