Adopting a Girlfriend or Mistress?

This is a bit tawdry.  A man who is being sued in a wrongful death case previously created a trust to benefit his 2 minor children.  He has now adopted his 42 year old girlfriend so she can be a beneficiary of 1/3 of the trust.  Assuming they remain a couple, she may use the trust assets to support herself and him even if he is forced to pay a large damage award in the lawsuit.  My trust documents are designed to prevent this because they provide that an adoptee must be younger than 18 to be considered a beneficiary.