It’s an attempt to feel the same way you were feeling while you were in a relationship with your ex.
It’s an attempt to have the same level of intimacy that you had with your ex, with someone else.
Of course, it’s not really a surefire way to determine whether or not they’re in a rebound relationship.
If they’ve been in the relationship for a few months or less, then it’s probably a rebound and it will end soon.
On the other hand, if their relationship has been going on for over a year, then you can safely assume that the relationship is serious for them and it’s probably not a rebound.
If your ex started dating someone else within a week of breaking up, then it’s more likely to be a rebound.
On the other hand, if they waited an appropriate amount of time (like three to four months) before entering the new relationship, it’s less likely to be a rebound.
If their behavior resembles that of a person in a rebound relationship, you can be know for sure whether or not you have a chance at getting back together.