Firslty, as per the information mentioned in the above query, makes it clear that though the two are separated from the father business, but still you all four have right in it.
Secondly, if one has taken loan then there are possibility that may be required to be paid back by all in equal proportion subject to some facts which need to be considered.
Thirdly, you should first apply for the succession certificate before the Civil Court of Law, that may take 2 to 3 months.
Fourhtly, then immediately file a suit for partition, and let the matter be handled by court of law.