Selling a land inherited from an ancestor long dead

My mom resides in a small rural village land owned by her family for generations. Its land title is still under the name of my mother's grandmother who has died more than 5 decades ago. After the death, it was passed on by consensus  to her surviving daughter (my mother's mother) for the payment of annual property tax and custody. My mother's mother died about 16 years ago and her immediate inheritors are her 10 children who are living in varied places in Philippines. Among the 10, it is only my mom who remained to live on their family land.

The family land used to be part of a larger coconut land, and has been categorized as such, but due to its small size, it can no longer be relied upon for cropping. Instead, my mother has been using it for vegetable gardening for her household use and for her housing.

Several years ago, my mother's siblings declared that they wanted to sell the land to my mom so that that they can get their share of inheritance. The problem is they could not agree on the price and people in the village are saying that my mom's siblings are being outrageous with the land pricing -- they are selling it at a price even much higher than those lots that are right along the village road and municipal road. (The location of my mom's family land is at the back of the village, with no access to the road.) The thing is, they are threatening my mother that they will either: 1. have the land sold to other people if she will not pay up their price, or 2. they will have the small land (less than 2,000 sq. meters) partitioned among 10 of them so that they can have their share.
We have consistently agreed to buy the land but they won't agree to the sale unless it is at the price that they had ordered.

My question is:
1. Can they indeed sell the land even if the title of the land has not been transferred from the name of their grandmother? How are they going to execute the deed of sale?
2. How much is the approximate cost of the transfer of land title (from my mother's grandma to my mother's mother to my mother and her siblings) with the inclusion of required taxes (inheritance, etc) given that the original owner of the land had already died more than 5 decades ago?

3. Can my mom (who has lived at and took care of the land, for close to 4 decades now, and has agreed to buy the land from them to keep the family land in tact) refuse to have the land partitioned?

4. Where do we go for legal remedy on this matter?

Thank you very much for bearing with me on this lengthy narrative and hoping for your help.

" Its land title is still under the name of my mother's grandmother who has died more than 5 decades ago."
Just checking, because it's some different if it's not.
Are you sure it's titled? Or is it just tax property?

1a. Can they indeed sell the land even if the title of the land has not been transferred from the name of their grandmother?
No, not if it's titled. To do that several steps is needed first.
They can't realy do it legaly if it isn't titled either, but then it's rather big chance to slip through.
1b. It's several steps,
but I better not tell how if they read here too

2a. How much is the approximate cost of the transfer of land title ?
There are both
/inheritance taxes (I don't remember how much but you can find it at http://www.bir.gov.ph/http//www.bir.gov.ph
/selling taxes and fees. (If I remember corect the total is some more than 10 %) of the highest of the selling price or the value the locaöl tax office find normal.
2b. original owner of the land had already died more than 5 decades ago.
I don't believe that make any difference. I asume BIR want to get paid anyway

3. Can my mom (who has lived at and took care of the land, for close to 4 decades now, and has agreed to buy the land from them to keep the family land in tact) refuse to have the land partitioned?
No.

4. Where do we go for legal remedy on this matter?
You can try PAO.
Perhaps Barangay Captain office assist some.

"The problem is they could not agree on the price and people in the village are saying that my mom's siblings are being outrageous with the land pricing"
You don't tell which province or if it's close to something which can raise the price as for instance a beach, so I can't know what's fair price. It's big difference between different provinces. In some places it's hard to sell for just 4p per squaremeter, while in other places it can be much over 40p.
Ask the local tax office for properties (=at barangay/municipaly office) how much they value such land to.

In many places it's hard to sell even for a fair price. If the sibblings demand much more than the value, then they can't sell it - except to a stupid foreigner (I'm foreigner, so I suppouse I'm allowed to joke like that

I PM you about one thing which I don't want to tell the sibblings if they read here

Dear Lunkan,

Thank you so much for your response.

Actually, I only assumed the existence of a land title based on a copy of the land document that was availed to me by the  Registry of Deeds (municipal), several years ago.  It bore the name of my mother's grandmother as the land owner, its land type  (coconut/agricultural land), its size measurement and appraised value. I have to check on that document again ASAP to see whether it was indeed the title.

I had also made an error about the land size -- it is less than 2,000 sq. meters and NOT 10,000 sq. meters (sorry about that..I had just re-checked it)

I greatly appreciate your care about discussing more details in the open forum. Will also PM you. More power!