Boric acid B(OH)3 and borates are a bit of a problem since boron likes to make B-O-B bonds. So the actual structures may be more complicated than the stochiometric formulas would indicate. If boron behaved normally you wound expect something similar to the following series of compounds which phosphorous exhibits; PO(OH)3, NaO2(OH)2, Na2O3POH, Na3O4P. As one goes from phosphoric acid to sodium dihydrogen phosphate to disodium hydrogen phosphate to trisodium phosphate the pH rises so that the trisodium salt is a very strong alkali almost as strong as sodium hydroxide. For borates with complex structures you simply cannot base alkalinity on the number of boron atoms in the molecule.
In the titration of boric acid you would expect to see a three step curve as each of the three OH groups is neutralized. However what is seen is a somewhat smooth rise in pH as NaOH is added. To see the steps clearly the simple sugar mannitol is added to the solution to break any B-O-B bonds. The boric acid then behaves more like a normal acid and exhibits a three stepped curve like phosphoric acid.