insert into an existing attribute in json with angular (nested json)

So in my application I have small blocks of info called suntis. Each sunti can have .tags, .author, .ancestor, .short_id, and some other attributes.

Say I have a sunti with the following

sunti_one = {
    content: "The nature of mankind is deep-down inseparable from the nature of the cosmos",
    tags: "philosophy, cosmos, nature, man",
    ancestor: "none",
    short_id: "H18EIQ5p"
}

Then I have a sunti with the following, where the ancestor field points to the short_id of the above sunti:

sunti_two = {
    content: "It's true that man and the cosmos are entertwined, but man is clearly embedded in the cosmos.  Yet, does that mean necessarily that the cosmos is embedded in man, too?"
    tags: "cosmos, entertwined, man, question"
    ancestor: "H18EIQ5p", << right here
    short_id: BkwV9q2a  
}

I want to check incoming suntis to see if they have an ancestor_id that exists already in my stash/cache of suntis-seen-so-far.

Now I have something like

socket.on('load_sunti_from_cache', function(a_sunti_over_the_wire) {

        angular.forEach($scope.suntis, function(single_sunti_in_stash) {

            //check stash'd sunti short_ids against incoming ancestor_ids
            //console.log(a_sunti_over_the_wire.ancestor + " \\\ over wire")
            //console.log(single_sunti_in_stash.short_id + " /// sunti stash")

            if (a_sunti_over_the_wire.ancestor == single_sunti_in_stash.short_id) {
                console.log('Matching ancestor & short_id: ' + single_sunti_in_stash.short_id)
                $scope.suntis. ...? (what do I put here so that the over_the_wire sunti gets appended as a descendent of the matching ancestor sunti?)
            }
        })

I want the result to be:

{
        content: "The nature of mankind is deep-down inseparable from the nature of the cosmos",
        tags: "philosophy, cosmos, nature, man",
        ancestor: "none",
        short_id: "H18EIQ5p",
        descendents: {
                      {
                      content: "It's true that man and the cosmos are entertwined, but man is clearly embedded in the cosmos.  Yet, does that mean necessarily that the cosmos is embedded in man, too?"
                      tags: "cosmos, entertwined, man, question"
                      ancestor: "H18EIQ5p"
                      short_id: BkwV9q2a  
                      }
                     }
 }