Taking your question literally:
Can? Yes.
You can file a lawsuit for any “reason” or no reason at all. Crazy and/or malicious people file crazy/malicious/frivolous/unintelligible lawsuits all the time.
Just because you can file a lawsuit does not mean, however, that you will prevail in court on your claim(s) made in your lawsuit.
So is it possible to find some plausible legal basis for a cause of action by one adult child against a sibling who helps one of their parents divorce the other? I’m sure it is.
Is it likely to succeed? No.
But could it? Possibly, depending upon the legal solidity of the bases for the claim(s), the skill with which the pleadings are drafted and the legal arguments are made, how persuasively you or your attorney argue the matter, and how receptive your judge and/or jury are to your arguments.
Utah Family Law, LC | divorceutah.com | 801-466-9277