Property lot problems

Hope someone can help me with this problem. I'm not really familiar about some related terms to this topic so please bear with me. I just want to seek a second advise on this matter.

I'm just going to give a detailed overview of our problem. Hope its not too long to read.

My family owns a lot which was not divided (not titles)among my mother and her siblings. My mother has 2 legitimate siblings and 1 adopted by my grandmother but with no papers (Uncle). My mother and her younger brother passed away a few years back and just recently my uncle as well. My Uncle (adopted) was married and was given a lot beside our house but no title on the lot. After his death, his wife sold the lot and claimed that it already has a title on it. Now the new owner of the lot has been harassing us and even cut off our water supply (deep well) because they claimed that it is part of their lot that they purchased from my uncle's wife.

Let me back track a bit. Originally my uncle (adopted) was holding the mother title of the entire lot before he passed away. When he passed away we try to acquire the mother title from them so we can have the divided lots titled individually. My uncle's wife refused to give it to us for no apparent reason. After a number of barangay sessions, they finally gave the mother title to us. We found out later on that she sold her husband's lot and claimed that it already has a title on it. The thought of it made me and my siblings decide to resurvey the entire property and have it titled and this time, not include my uncle (adopted) on it. So basically we divided the lot and have it titled with all the legitimate persons on it.

We are still on the process of waiting for the titles as of the moment. We tried to send a notice to the new owner to stop construction on the lot or legal actions may have to follow. They ignored it and instead barricaded the lot from our house; cut out main source of water supply and even insists on going to court.

Here are my questions:

1. When they had the mother title before, is it possible for them to just choose a portion of it and have it titled?

2. We can exclude my uncle on the process of having the divided lots titled because he is not considered a legitimate part of the family right?

3. If indeed true that the new owner has a title of the land, can it still be considered null and void? (excuse my term)

4. The new owner of the lot like I said, cut off our water supply and placed a barricade on their lot. Can we do something about this one? We have not seen the title of their lot and they are already doing these things.

I think that sums it all. I hope someone can advise me with this problem. If anyone has anything to say please don't hesitate to reply to this one.