It's an oversimplification of course, but let's try another oversimplification just for argument's sake and to highlight the mechanism.
Let's say you are born without parents, and your parents get picked at random once you enter university (a completely fair system in that there is no bias involved).
If 4% of all "available" parents have a degree, your chance that you'll get at least one of those "assigned" to you is 7.84% (1 - ((1 - 0.04)^2)).
If 14% of all parents have one, this probability rises to 26.04% (1 - ((1 - 0.14)^2)).
Let's say you are born without parents, and your parents get picked at random once you enter university (a completely fair system in that there is no bias involved).
If 4% of all "available" parents have a degree, your chance that you'll get at least one of those "assigned" to you is 7.84% (1 - ((1 - 0.04)^2)).
If 14% of all parents have one, this probability rises to 26.04% (1 - ((1 - 0.14)^2)).