Log4net to logstash

I'm trying to get a log like this from log4net:

[27][14:08:36.584]
[{"name":"Vinicius","SerialNumber":"957593196"}]

[37][14:08:36.584]
[{"name":"Mylonas","SerialNumber":"957593166"}]
...

How can I get this information from these three fields in two lines? Is there any pattern in grok for this?

filter{
  grok {
    match => {
      "message" => ["\[%{NUMBER:threadId}\]\[%{GREEDYDATA:sourceTimestamp}\]"]
    }
    match => {
      "message" => ["\[%{GREEDYDATA:json_data}\]"]
    }
  }
  json{
    source => "json_data"
  }
}