Your relationship will probably have fewer bumps if he learns it directly from you.
Send an email or text to your ex and ask to schedule a time for the two of you to chat.
Tell your ex before the kids know, suggests Laura Campbell in a “Huffington Post” article, “It’s Not Communication, It's ‘Ex-Management,’" otherwise the kids might deliver the news for you in a less than ideal fashion.
Explain to your ex that you are dating and provide some details about the person you are seeing, such as how long you have been seeing her, where you met her, if she has children and her name.
If the kids haven’t met her, let your ex know that as well so she won’t assume that the relationship has gone further than it has.Ask your ex if she has suggestions about guidelines such as not including the new girlfriend in family activities, no sleepovers while the kids are there and limited public displays of affection.Focus the conversation how to make things easier on the kids adjusting than about the girlfriend, suggests Help Guide.Be considerate and respectful so that your interaction remains calm and cooperative.
If your ex was holding out hope that you might reconcile, he also wants to know when you are dating.
If you don’t tell your ex, he could learn about it from your kids, family, friends, or from your social media page.