Composite Entity Inheritance question

How can I use two Entities with a Composite relationship as Parent (inherate) to two other child entities respectively?

For example, I have two Entities: SalesOrder and SalesOrderLine where SalesOrderLine is composite to SalesOrder.
When I extend

  1. SalesOrder2 extended to SalesOrder
  2. SalesOrderLine2 exyemded to SalesOrderLine

Then I don’t get any additional field I add to SalesOrderLine2 entity through SalesOrder2 entity. How can I resolve this issue, thanks for any suggestions?