Summons to attend and parties to proceedings
45Where proceedings are taken for proving a will in solemn form or for revoking the grant of letters probate of a will on the ground of the invalidity thereof, or where in any other contentious cause or matter the validity of a will is disputed, all persons having or claiming to have an interest in the property affected by the will may, subject to this Act and the rules, be summoned to attend the proceedings and may be permitted to become parties, subject to the rules and to the discretion of the Court.