three lists, two parents one child lookup relation

Question

I have three lists, parentListA, parentListB, childList

Example of parent A:

parentListA = {
  ID: 1,
  Title: 'a parent',
  Description: 'lorem ipsum'
}

Then I created the child list, so naturally I created a 'lookup' field to parentA

Example of child:

childList = {
  ID: 1,
  Title: 'a child',
  Description: 'lorem ipsum',
  ParentId: 1 // lookup field to parentA
}

Now I need to create another parentList, which has the same child list as the first parent, but the child list now has a lookup to the first parent (as it should, as well as to the new parent)

How can I connect a child list to two parent lists?

obs! Both parent lists should be connected to the same child list, but a child item can only be related to one parent item (so a child can't have a parent from both parent lists) .. I hope I make any sense :)

Answer 1

An alternative is to add two content types to the child list. Then you can remove the lookup field for each type of content.

Steps

1. Create two content types (ParentA, ParentB)
2. Enable content types on your list and add this content types
3. Edit each content types on the list and hide de loockup column

Tutorial: http://www.sharepoint-journey.com/create-content-types-in-sharepoint-2013.html