Dan found out that I had been meeting my ex-boyfriend in secret.

丹发现了我一直和前男友秘密见面。

《柯林斯英汉双解大词典》

I recently spoke to a friend who had a huge fight with her boyfriend because he met an ex for lunch.

我最近刚刚跟一个朋友聊过天，她跟男友大吵了一架，因为他跟前女友吃中饭。

youdao

I spent less time with my friends because going out with the group meant I couldn't bring my new boyfriend since his ex would be there.

我花很少的时间和我的朋友在一起，我不能带我的男朋友和他们一起出去因为他的前女友可能也会在。

youdao

No immortal lines this week, and my boyfriend, or ex-boyfriend, I should say, has decided that our poetics are incompatible.

NEWYORKER: Deniers