Partition of Property Between Son & Daughters

My Husband is a only son with two younger sisters, the first sister is married and second sister is yet to be married. During the time of first sisters marriage we have given a dowry like, Cash, Jewellery and 20X30 Plot (outskirts of Bangalore). Now we are planning for second sister now the first sister is demanding for a different plot which is in the city centre which values more (Money Wise). All the property which I'm talking is owned by my FIL, Second sister who is to be married is in love with her BIL's Brother, so the first sister husband is demanding for property and dowry and he is mentally harassing our in laws. If the demand is not fulfilled he will not agree for the marriage of his brother with my SIL. Now, my FIL also have some liabilities and he doesn;t have any cash in hand for marriage, so he has to take a loan for marriage as well. If we give the property to both the daughter as equal share of that son. Do the loan & liabilities availed by my FIL will be borne only by the son. And my FIL's health is also not in good condition what on the expenses borne for his health. And we have two childrens who are still minor, do they have any rights on their grandfathers property, as a natural guardian of my children can I take any stand on this regard. Please reply