In what capacity your father/ family is holding possession such as tenant / succession / relative etc. ?
What is the order / judgement passed against your father, which is stated to have been challanged ?
The facts posted by you suggest that your case is, prima facie, very weak since the Trustees [owner] do not want your father / parents/ family to continue possession.
What is the opinion and advise of the lawyer engaged by your father as s/ he [lawyer] is well aware about facts and circumstances of the case and an able, competent and intelligent enough to satisfy your queries ?