Spawning an asset nearby group of assets

Question

I am spawning a bunch of assets randomly on my map and then spawning 4 random positions on the map which I will use to calculate the closest assets to those four random positions to "group" or "cluster" the assets. My goal is to have each group/cluster contain at least 1 of each asset. This is where I seem to be going wrong and I cannot seem to figure out how I could add an asset to a group/cluster by spawning it nearby the rest of the assets its grouped

Added the full spawning and clustering script to pastebin which may help build a better understanding.

SpawningAssetsAndClusteringScript.cs

Spawning all assets method

SpawnAssets = new List<GameObject>() { Tree, Coin, HealthPot, Enemy, Weapon, Trap1 };
//...
public void SpawnEveryAsset()
{

int TotalAmountToSpawn = 30;
int TotalAmountOfAssets = 6;
int TotalAmountToSpawnOfEach = TotalAmountToSpawn / TotalAmountOfAssets;

for(int i = 0; i < SpawnAssets.Count; i++)
{
    SpawnAnAsset(SpawnAssets[i], TotalAmountToSpawnOfEach);
}
}

// Instantiate the asset
void SpawnAnAsset(GameObject AssetToSpawn, int amount)
{
    for (int i = 0; i < amount; i++)
    {
        var pos = RandomPositionOnTerrain();
        var spawned = Instantiate(AssetToSpawn, pos, Quaternion.identity);
        SpawnedAssetsInLevel.Add(new Asset(spawned, pos));
    }
} 

Random position on terrain that is valid to spawn an asset

Vector3 RandomPositionOnTerrain()
{
    var x = UnityEngine.Random.Range(0, GridData.Width);
    var y = UnityEngine.Random.Range(0, GridData.Height);

    var NodePosition = GridData.grid[x, y];
    if (NodePosition.terrainType == TerrainType.Grass || NodePosition.terrainType == TerrainType.Sand)
    {
        if(!GridData.IsCellOccupied(NodePosition))
        {
            Vector3 LocationToSpawn = new Vector3(NodePosition.Position.x, (NodePosition.Position.y), NodePosition.Position.z);
            
            assetSpawnLocations.Add(LocationToSpawn);

            GridData.Obstacles.Add(NodePosition);

            return LocationToSpawn;
        } else
        {
            var pos = RandomPositionOnTerrain();
            var NodePos = GridData.grid[(int)pos.x, (int)pos.y];

            assetSpawnLocations.Add(pos);
            GridData.Obstacles.Add(NodePos);
            return pos;
        }
    } else
    {
        var pos = RandomPositionOnTerrain();
        var NodePos = GridData.grid[(int)pos.x, (int)pos.y];

        assetSpawnLocations.Add(pos);
        GridData.Obstacles.Add(NodePos);
        return pos;
    }
}

Example output: Tree and Trap are 0 in this group/cluster so I would want to spawn a tree and a trap nearby these other assets.

Cluster1:
TreeAmount: 0
HealthPotAmount: 1
EnemyAmount: 2
Trap1Amount: 0
CoinAmount: 1