Represent union of classes

Hi All,
iam new to UML,
kindly help in one of the problems.

i have the following classes
1 class Holder which contains holderNumer as attribute
2 class Participant which contains participantNumber as attribute
3 class Account which contains accountNumber as attribute

now there are many classes in my project which use the above three class as key.

but it is very tedious to declare all three class objects in the different classes when we look at programming point of view.

i think, i should have another class called Key and declare all the above objects in this class and use this class object instead of 3 class objects.

i think the above solution is ok, but how to represent this in UML diagram.

or suggest me the alternate solution for this problem.

Thanks in advance