It is extremely hard to have specific comments in situations like this as there is a lot that goes into making assessments and it's hard when only a small part of the picture is available. That being said, here's what I do know:
Lipoprotein (a) or Lp(a) is primarily genetically determined and highly inheritable. Levels are primarily determined by a specific gene found on chromosome 6q26-27. It is not easily modifiable with lifestyle changes or even drugs. That being said, there are a few situations that might elevate Lp(a) beyond the levels that are determined genetically. Low estrogen levels, uncontrolled hypothyroidism, uncontrolled diabetes, and familial hypercholesterolemia. High levels of Lp(a) is a possible risk factor for the development of cardiovascular disease. Given that it is hard to treat, therapy to reduce the CVD risk should focus on the other risk factors for CVD that are more treatable. This would include LDL.
In summary, unless these patients are dealing with some of the associated conditions mentioned above, there's probably not much to explain the elevated levels of Lp(a) other than genetics. Levels may fluctuate but look to treating other modifiable risk factors of CVD if you suspect that the elevated Lp(a) poses an increased risk.