1. No maximum or minimum lot size.
Before transfer, re-cutting must be done. Hire a geodetic engineer, he/she will produce a technical description which goes through the Bureau of Lands (to put it very simply). It's not a short process. Then the technical description and old title, together with the real property tax receipt will be submitted to the Registry of Deeds to produce two titles, still in the name of the original buyer.
Your brother may then transfer the other title in your name. You may opt for either Deed of Donation or Deed of Absolute Sale. If your brother has heirs, it could be a different scenario altogether, in which case one may suggest a Deed of Absolute Sale instead.
2. Sec 7 RA 26 states that the title is reconstituted from a lost title.
You may ask for more help from the nearest Registry of Deeds to give you accurate information. Order a certified true copy of the title while you're there.