Is it bad if your best friend dates your ex?

If your friend still has feelings for their ex and had told you so, thats a red flag that dating this person is a bad idea. It can be tough to move on from a relationship when those feelings still exist, and it could cause tension if you make a move before your friend has moved on.

Is it okay to be friends with your friends ex?

Talk to your friend: If the friendship between you and your friends ex happened because of your friend, its important to check with him or her, if they are fine with you staying in touch with their ex. If your friend doesnt approve of you socialising with their ex, try reducing such interaction.