chalilavachus- -I feel your pain. As someone who has a sibling OTD (also very intellectual) I can tell you one thing, It is NOT the parents fault. I saw some people write that they find it hard to believe that it is not a disfunctional family. I am telling you that it is not as uncommon as people think. Yes there are risk factors but many “normal” famlies have been hit with this maka.
In my siblings case, my parents did all they could for the child. As a sibling I can see nothing that my parents did wrong. This is from a time prospective (over ten years!)For a while some of the siblings managed to keep a realationship but today we rarly have anything to do with the sibling as everytime we spoke it came down to “prove there is a G-d”.
If the child needs $$$ perhaps come to an agreement about a weekly/monthly sum. This might give over the feeling that you care about them without your feeling that it is a bottomless pit.
We were very lucky that when the sibling was at home they did not try to influence other childer. If this OTD child is influencing the other children perhaps you need to offer to pay for rent for them. However take into account that this might backfire to “you are kicking me out of my home and dont care about me”
In fact I can imagine that most anything you do will end up being twisted to the OTD child’s liking. So keep in mind that you need to take YOURSELF and the rest of the family into account as well. Dont “ignore” your needs or other childrens needs because you are afraid of alienting the one child. Sometimes you can never get things right (especially with this kind of child)And no a therapist is not going to happen with this kind of person. I know that only to well.
I know it feels like the pain will never go away, Just keep reminding yourself that everyone has bechira and that although you gave this child the tools to make the right descions he/she has chosen otherwise and it is not reflective on you as a person or as a parent.