First, if he's talking about her on a regular basis. It's quite normal for a person to mention the ex. It's okay for them to even mention their likes and dislikes, usually mentioned in the first month or two of dating and done in moderation; however, if she is the topic of the day, everyday or every other day, he's not over her.
Second, if he gets upset when you tell him that he's not over her. When you're over someone the simple mentioning of her name would go in one ear and straight out the other. It wouldn't strike a nerve, clinch fist and raise eyebrows.
Third, if he calls her everything but a child of God. Congratulations! You are dating, the Jeopardy winner on the topic of name calling. I'll take "Name Calling" for 200 please, Alex. If they have children together, this is definitely not a good sign. It shows a lack of respect, a lack of maturity and a sure fact that he will refer to you as the same in the near future. No one should make you that upset that you have to result to name calling.
Fourth, if he still has pictures and keepsakes from their relationship. Wow! She won that bear for him at the fair. He likes the way he looks in that picture. He was muscular and thinner back then. Well, join a gym. The focus should be on the new relationship with you. Not the past relationship with her. That certainly wasn't the end of all fair's.
Fifth, he still has a special ringtone for her. The question that comes to mind is—why? You should be the only one with a special ringtone. Sure this may sound trivial, but it's another clear sign that—he's not over her. He's eager to hear the ring and is preparing himself for the call. No, he's not brushing his teeth or combing his hair. He's preparing mentally.
Sixth, he tries his best to get even with her. Again, the question that comes to mind is—why? If all of his energy is spent on ways he can get even with her, when is he spending quality time with you? Time shouldn't be physically spent together but mentally and emotionally as well. You don't just want his body with you, but his mind and heart too. If his mind is somewhere else his heart may be there too. It's a thin line between love and hate. Usually a person can hate someone because they love them, and hate the fact that they don't love them back. Love and hate basically stems from being hurt.
Seventh, if he talks negatively about her to the kids. This is obviously something that should never occur. His disagreement is with her, not the kids. Kids love their parent's not matter what they do. They will always love them. Putting negative impressions about her in their minds will make them resent him in the long run. This should raise a red flag with all women. The way he talks about her will be the exact same way he will talk about you if or when you become the ex.
Ladies, these are a few good signs to look for. He's subconsciously informing you that he's not over her. There are still some unresolved issues that he will have to finish before the two of you can continue and grow as a couple. It's okay if he's not over her. Don't look at it as a reflection on you, she was before you. Therefore, you have to ask yourself, do you want to be number one? Number two? The only one? If your answer is the only one, then you'll have to wait until he ends his unfinished business. But don't wait too long, because there are other men who will love to have you as his only one.