If all his at least more recent kids are IVF as rumored then I would entirely expect him to select for XY embryos because it is "manlier" or some such bs. Anyway as each kid is a separate 50% chance for XX and XY it is still quite possible for this to occur naturally just low probability to occur in a row and we know nothing about whether any miscarriages have occurred to his "partners".
I was talking about this with some friends the other day and I was made to look ignorant as apparently it's simple to 'select' a boy if you are conceiving IVF, is that not the case?