GeoJSON cluster, group points with the same id

Question

I want to make a cluster with a GeoJSON, to obtain the file I query a table in PostgreSQL and I save the file. The same point can have several associated images, but according to the GeoJSON, it makes a record for each one and the cluster understands it as independent points. If there are several images at a point, can they be grouped into a single feature? It's my sample GeoJSON, you can se the id_observation 51, is the same observation with two images

{
    "type":"Feature",
    "id":22,
    "properties":{
        "a_code":"151",
        "name":"one Name",
        "id_observation":"51",
        "long_4326":"-x.xxx",
        "lat_4326":"xx.xxx",
        "obs_date":"2015-03-17",
        "id_observation_font":"1",
        "id_image_observation":"30",
        "main_co":"f",
        "author":"John",
        "image":"data/IMG1.JPG",
        "geojson":"{\"type\":\"Point\",\"coordinates\":[-x.x,xx.xx]}"},
        "geometry":{
            "type":"Point",
            "coordinates":[-x.x,xx.xx]}
    },
    {
        "type":"Feature",
        "id":23,
        "properties":{
            "a_code":"151",
            "name":"one Name",
            "id_observation":"51",
            "long_4326":"-x.xxx",
            "lat_4326":"xx.xxx",
            "obs_date":"2015-03-17",
            "id_observation_font":"1",
            "id_image_observation":"29",
            "main_co":"f",
            "author":"John",
            "image":"data/IMG2.JPG",
            "geojson":"{\"type\":\"Point\",\"coordinates\":[-x.x,xx.xx]}"},
            "geometry":{
                "type":"Point",
                "coordinates":[-x.x,xx.xx]}
    },
    {
        "type":"Feature",
        "id":24,
        "properties":{
            "a_code":"715",
            "name":"other name",
            "id_observation":"52",
            "long_4326":"-x.xxx",
            "lat_4326":"xx.xxx",
            "obs_date":"2015-06-01",
            "id_observation_font":"1",
            "id_image_observation":"31",
            "main_co":"t",
            "author":"Phill",
            "image":"data/IMG32.JPG",
            "geojson":"{\"type\":\"Point\",\"coordinates\":[-x.x,xx.xx]}"},
            "geometry":{
                "type":"Point","coordinates":[-x.x,xx.xx]}
    }

This is my sample query

$query = "Select a_code, name, id_observation, long_4326, lat_4326, obs_date, id_observation_font, 
id_image_observation, main_co, author, image, ST_AsGeoJSON(geom, 7) AS geojson FROM observations WHERE id_observation_font != 3 ORDER BY id_observation";

$result = pg_query($query) or die('Query failed: ' . pg_last_error());
$geojson = array(
    'type' => 'FeatureCollection',
    'features' => array()
);
$i = 0;
while ($line = pg_fetch_assoc($result)) {
    $feature = array(
        'type' => 'Feature',
        'id' => $i++,
        'properties' => $data[]=$line,
        'geometry' => json_decode($line['geojson'], true),
    );
    array_push($geojson['features'], $feature);
}
$localiza = json_encode($geojson, JSON_UNESCAPED_UNICODE);
$conta = "../data/observations.json";