You can set an asset as a child of a User Defined Object.
Navigate to a user defined object type (UDOT) and click the Relationships tab.
Under the Child Object Type column, select an asset type.
Under the Relationship Name column, set the relationship name.
Under the Relationship Multiplicity column, select how many assets you are able to associated with that specific UDO. For example: 0..* , 0..1.
Navigate to an asset, and on the action toolbar, click Modify Relationship.
From the drop down, select the the relevant Add to UDO action.
Click the Configuration Options drop down.
From the Parent User Defined Object field, select the UDO you want to associate the asset with.
In the Parent User Defined Object field, enter the ID of the UDO you want to associate the asset with.
Click Run Now to complete the job.
Navigate to the object hierarchy and you will see a link to the asset underneath the object.