Acquiring property (lot)

We are planning to purchase a lot somewhere in Bulacan. The lot is originally owned by three siblings. In the title it was mentioned that the lot was owned by Mr.____spouse of ____, so on and so forth. Now, the children of these three original owners are interested in selling the property while their parents are still alive.
I had a copy of the title, and had it checked in the local registry of deeds. We saw remarks at the back that the registry issued two co-owners copy of the title. When we are asking for the copy of the 2 co-owners copy from the seller, they told us it was lost. Only one owner showed us a copy and that was the one we had checked with the registry.
If I want to buy the property, what are the documents and procedures that I need to know to acquire the lot legally and without future hassles. Is it okay that they only show one title, since they cannot retrieve the other 2. How will I be rest assured that the lot is not sold by the seller to other parties? Prior to buying, what are the legal steps do I need to know.
Appreciate your help on this matter.

i tried to research your question but i could not find a definite answer. i believe the register of deeds will require the submission of all the deeds of sale.

if it has been sold to someone else and that someone was given the missing title, you will be considered in bad faith because you had notice of the other copies of the title.

have the owners petition the court for reissuance of the missing titles before selling to you. it will the safest way to proceed.