Propser is basically right you could try, but courts are very reluctant to take custody away from parents especially if child services has not been involved up to this point. There have been quite a few cases like this and generally the parents prevail, but you would need to prove the father is a drug addict with documentation and the rehab etc which might be confidential. Furthermore, judges do not like to order kids to move across the country either as kids have friends, teacher, familiarities, transitioning a child across country can be very hard on them particularly if it has to happen again when the parents recover.
If you really believe it is in the best interest then you can fight for it, but this might sever any relationship you have with the parents of the children and there is a good chance you will lose. However, I am just an anonymous internet poster like anyone else on this board that knows nothing about you, the situation, or all the details. It is possible just a big uphill battle there are several places to find a lawyer to speak to I would start with the Oregon state bar website, this site can help you, or legalmatch, or any number of places allow you to find an attorney to handle your situation. Hopefully whatever happens everything works out for the best good luck.
