Below is a simplified version of my more complex problem. Changing the table structure is not an option.

I have a model called CostData:

• My app can have “duplicates” of CostData that can later merge into one another (biz logic).
• This is a parent / child relationship, where parent is the original CostData model and child is the duplicated CostData model.

The cost_data table looks like so:

id | amount
1    2000.00
2   -1000.00

I have a model called MergeLink:

• The merge_links table tells us how CostData models (and many other unlisted models) should merge to one another.

The merge_links table looks like so:

id | mergeable_type         | parent_id | child_id
1    "AppModelCostData"     1           2

In Mergeable trait used by CostData model (and many other unlisted models), I have:

trait Mergeable
{
    public function merge_link_parent(): MorphOne
    {
        return $this->morphOne(MergeLink::class, 'merge_link_parent', 'mergeable_type', 'child_id');
    }

    public function merge_link_children(): MorphMany
    {
        return $this->morphMany(MergeLink::class, 'merge_link_children', 'mergeable_type', 'parent_id');
    }
}

This gives me back the correct MergeLink when accessing merge_link_parent or merge_link_children on a CostData model.

Now, I want to go one step further and return the mergeable_parent or mergeable_children relations, possibly using the merge_link_parent and merge_link_children relations respectively. See below Tinker pseudocode.

$costDataWithParent = AppModelCostData::find(2);
$costDataWithParent->mergeable_parent;
// Should return:
// {
//    id: 1,
//    amount: 2000,
// }

I would like to do this via a relation (not an accessor).