You should file a custody action and demand that no contact with his paramour be made a part of the order. I will say, that unless the paramour is a sex offender or an extremely negative influence on the kids, the likelihood that the court will grant your request is slim. Kids may be affected negatively by exposure to a parent's new significant other. However, at some point, the children are going to have to be exposed to the fact that mom and dad are no longer together and that someone new may be in the picture. I would and have typically cautioned all my clients never to bring new significant other into the picture unless and until I know that it's going to be a commited relationship. It's not fair to the kids and may be injurious to them as well.
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