Highlight produce unexpected invalid results on multivalue fields copied from other fields

Elastic Stack Elasticsearch
1

Steps to reproduce

  1. create mapping
post /test/_mapping 
{
    "properties": {
      
      "family": {
            "type": "text",
            "index": true,
            "term_vector": "with_positions_offsets",
            "store": false
      },
      "person":{
            "type": "keyword",
            "index": true,
            "store": true,
            "copy_to":["family"]
      },
      "sisters":{
            "type": "keyword",
            "index": true,
            "store": true,
            "copy_to":["family"]
      },
      "brothers":{
            "type": "keyword",
            "index": true,
            "store": true,
            "copy_to":["family"]
      }
    }
}
  1. post a document
POST  /test/_doc/1
{
  "person":"john doe jr",
  "sisters":["pam doe jr","ann doe older"],
  "brothers":["peter doe jr third"]
}

3 Perform search

POST /test/_search
{
  "query":{
    "match": {
      "family": "doe jr"
    }
  },
  "highlight": {
    "fields": {
          "family": { }
    }
  }
}

Unexpected invalid results of highlighter

"highlight": {
          "family": [
            "john <em>doe</em> <em>jr</em>",
            "pete<em>r d</em>o<em>e </em>jr th<em>ird</em>",
            "a<em>nn </em>d<em>oe</em> older"
          ]
        }
2

Forgot to mention server Version is 8.4.1

Please, Can anybody check and confirm this bug