I'm pretty sure Global knives come from the factory with a flat bevel and not a convex edge. I believe the factory angle is something slightly more acute than 15* (have seen a lot of different numbers).
Global recommends that customers sharpen their knives to a flat bevel at between 10* and 15*. Global's pull through sharpener the "MinoSharp" is set at 15*. Global's MinoSharp angle guides will result in a 12* - 15* flat angle when properly attached. Global's sharpening expert, Mino Tsuchida, aka Mr. Global, recommends 15* - 20* flat.
Multibevel geometry can be a good thing on some knives, and for all I know the geometry Ben recommends is perfect for Globals but I think it's too much to ask someone like Bjarkib, who is pretty much just starting out, to sharpen five separate bevels at three separate angles.
If he can clean up his relatives' knives and get them to the simplest possible edge, a 15* flat V, with good sharpness, that's a very good thing for all concerned.
Save the fancy sharpening until you're really consistent with the simple stuff.