Probably half the military is Russian.
The other thing is this: I remember during the invasion of Iraq that one important thing we did was to have relatives of various Iraqi generals contact them and make offers of cash (a million or two each as I recall) and green cards and residency in the US for them and their whole family if they would defect or at least stand down during the invasion. Lower ranking officers received similar offers of less money and residency in other Gulf states. Don't know how many took the offer.
The other thing was making it public that we were doing it, so that the Iraqis would suspect one another of taking the offer.
So I can't help but wonder if in Ukraine these kinds of offers are made under the table, or if this kind of thing is spread just so the Ukrainian officer corps would not know who they can trust. Cheaper to pass bags of money under the table than to have to fight. And in this case they are cousins and formerly citizens of the same country.
Some reports say that Ukraine hasn’t had money to pay their soldiers, so probably just getting paid would be motive enough for some of them.