[Solved]-Populating Highcharts tooltip with data from other charts-Highcharts

You can define the tooltip structure in the pointFormatter function, for example in this way:

 pointFormatter: function() {
   var thisChart = this.series.chart,
     pointIndex = this.index,
     point,
     result = '';

   if (thisChart === Highcharts.charts[Highcharts.hoverChartIndex]) {
     Highcharts.charts.forEach(function(chart) {
       point = chart.series[0].points[pointIndex];

       result += '<span style="color:' + point.color + '">●</span> ' + point.series.name + ': <b>' + point.y + '</b><br/>'
     });

   } else {
    result = '<span style="color:' + this.color + '">●</span> ' + this.series.name + ': <b>' + this.y + '</b><br/>'
   }

   return result;
 }

Live demo: http://jsfiddle.net/BlackLabel/6m4e8x0y/4814/

API Reference: https://api.highcharts.com/highcharts/tooltip.pointFormatter