Estate Law Questions? Ask an Estate Lawyer.
This is probably not going to be the answer you wanted, so please don't shoot the messenger.
You own only 1/4 of the house, but have had 100% of its use. I realize you have been paying the taxes and doing upkeep, but your other three siblings could have also demanded that you pay 3/4 of the market rent. Had you not been living there, the property could have been rented and the proceeds divided 4 ways.
The short answer is that they are within their rights to demand their money and can force the sale of the property. If you want to keep the property, buy them out - secure a mortgage for 3/4 of the value of the property and pay them off.
I hope this helps.