Sale Of Property

The owner of the apartment is in my name, my mom's and my brother's. he is a minor-aged 17. the document states that the sale of the flat cannot be done until he turns 18. However, due to financial constraints, we need to sell the property. what I mean by financial needs is that my parents, my mom and my dad have been separated for 5 years and in that time.. my grandmother (mother's mother) had been taking care of us financially. she passed away in July and we have no income as of now and the only property we have is the subject one in question. my father doesn't support us financially. My brother needs to go to college next year and my mother doesn't want to depend on anybody financially especially when she has a home that she can sell and is in her name also. when all the joint owners aka my mother, me, and my brother who is a minor are okay with selling the property, can we? also, if the buyer agrees to the sale despite knowing the clause in the document, is it permissible? is there a work-around of this clause? will it affect the sale of property and if a no objection letter is gicen by the other two owners namely me and my mother, can we sell?