you ok mahhh???
i can understand his eldest sis's position..what she did is not wrong,she is the eldest and also she is married.she can no need to contribute anything but bcos that is her mum and 2 younger siblings, she has the responsibility..
since your hubby is the only son...i believe your hubby have to catch the ball...to support his family as a son.now the main concern is the younger sis and the expenses incurred in your family if they will to move in to your house..
is his eldest sis confirm selling the house or just rent out?
if sell,does your hubby gt a share from the profit? is yes,then he has to use it for supporting this family member.