Untitled

let inputArrayObj = [
  // your input array objects here
];

let outputJsonArray = [];

for (let i = 0; i < inputArrayObj.length; i++) {
  outputJsonArray.push(inputArrayObj[i]);
  if (inputArrayObj[i].relative === true) {
    outputJsonArray.push(inputArrayObj[i].relativeTypeDetails);
  }
}

console.log(outputJsonArray);