Grand father property with out partitioned

A sale of undivided interest can be made to a third party if the co-sharers reach a settlement for Partition of the said property by metes and bound and give an NOC for the same. In absence of division by metes and bounds, a sale remains valid and only the possession of joint estate cannot be enjoyed by the ytansferee unless the property which is subject matter of sale has a character of exclusivity.Where a share in a dwelling house belonging to an undivided family is transferred to a stranger; the transferee cannot claim joint possession or any common part or enjoyment of the house. He can enforce his right over the property by a suit for partition.

 Therefore if your cousin brother tries to irritate you by giving such threat,then tell him that even when he will transfer his undivided share in the dwelling house to any rowdy person just to compel you to live with that rowdy person in the same dwelling house,even then your cousin's mala fide motive will not be fulfilled until and unless that rowdy person as stranger purchaser by filing Partition Suit separates his portion and at that time you will get the opportunity to exercise your pre-emptory right as the shareholder of that dwelling house to repurchase that share from that rowdy person at and for such consideration so to be decided by the Court of Law in that Partition Suit.If in the Partition Suit,none of the existing shareholders of the dwelling house undertakes to exercise the preemptory right to repurchase,even then it is upon the Court's discretion,whether to allot that stranger purchaser the portion on main road which is presently under the occupation of your cousin brother because the Court will consider your pleas also claiming the main road side of the dwelling house. 

 If you have evidence in your support that your cousin brother is trying to cause harm to you ,then you can.