Hibernate inserts duplicate child on cascade

At times we all use hibernate's cascade feature to cascade the child entries into database for OneToMany and ManyToMany relationships. If it is a first entry in DB then everything works fine but when we want to update the number/quantity of child of an existing parent, hibernate adds duplicate children. Assume the parent already exists with few children. Below is the relationship:

Parent Mapping for OneToMany with Child:

@OneToMany(targetEntity = ChildrenImpl.class, mappedBy = "parent", orphanRemoval = true, fetch = FetchType.LAZY)
 @Cascade(value = CascadeType.ALL)
 private List<Children> children = new ArrayList<Children>();

Child Mapping with parent ManyToOne

@ManyToOne(targetEntity = ParentImpl.class, fetch = FetchType.LAZY)
 @JoinColumn(name = "PARENT_ID")
 private Parent parent;

Below is the code which leads to duplicate children.

Children newChild = new ChildrenImpl();
 newChild.setName("I am a new child");

 /* More setters here */

 ...

 parent.getChildren().add(newChild);

 /** More business logic here **/

 entityManager.merge(parent); // OR session.merge(parent); whatever implementation exists

At this point if you check DB, there will be 2 rows for this new child. To solve this problem there are 2 ways:

1) Update the mapping annotation to load the children in parent eagerly using fetch = FetchType.EAGER at @OneToMany

2) Just before adding the new child into the existing child list/set, load the existing children forcefully by calling size() or any operation like isEmpty() which leads to load entire object in memory of that List or Set.