A lot of divorced parents don’t want anything to do with their exes’ «other family,» and I don’t begrudge them for that. If the divorce was amicable and a parent is involved in their children’s half-siblings’ or step-siblings’ lives, that’s all well and good. As long as they can do that without resenting the kids they are interacting with on a day-to-day basis, it can be a healthy arrangement. However, the majority of divorces are not all rainbows and sunshine, and adults who do not want to interact with children they can’t help but resent may be the healthier option. It’s better not to interact with your ex-husband’s affair baby because you know you cannot look at her without thinking about his betrayal. It’s not the kids’ fault that they were born under such circumstances, so it’s probably better that they are protected from the hostile glance of adults who resent their existence.