I disagree. If you break down stories with problems its only a handful of things on the general level that are the motivations. Family, money, power, friends etc. So 4-6 out of 12? being about family problems is kind of normal.
I disagree, survival (from a non parental unit), wanting to keep a secret that could harm (Mordin), National or other group loyalties (Legion), Revenge (jack and Garrus), Also the ones he counted were daddy issues, siblings, and distant family or family ties were much more rare, heck even mother issues were pretty rare. Wanting something personal (kasumi)
Add in that these issues were often because of an absent, cruel, or distant relation how many family members did we need to rescue? 2! one from a mean dad and another because the character was a distant father. Not counting Morinth because she was to be killed but still counts under cruel.
Also an idealogy can be a good motivation. Doing something to help a group of people they are apart of/ agree with is a totally acceptable quest. And even if you can fit all of these into 4 simple catagories, the fact a majority is one very specific kind of a motivation while the others are varied, kinda points out it is overused.
I like my companions to have family that are not wayward children and evil/distant fathers. Garrus and Ashley's sisters are way more interesting than Kolyat to me. Kaiden, Garrus, Ashley's parents could make for great motivations (because we know they care about them.) Mordin's nephew could also be a good inspiration also. But the variety on family motivations would be nice.