Does 6-methyl-2-(methylamino)pyrimidin-4-ol show aromaticity?
Each Nitrogen has 5 valence electrons. They are using 2 of those in sigma bonds to their neighbouring atoms, 2 in an sp2 lone pair in the plane of the ring, leaving only 1 electron to contribute to the delocalised pi system. 

Each carbon is also contributing 1 electron to the delocalised pi system, and has 3 involved in sigma bonds.

This means each member of your 6 membered ring is contributing 1 electron, 6 in total. This means it is aromatic, as all 3 bonding orbitals are fully occupied.