JSFiddle - React, Tailwind, and code Playground

HTML

<pre id="result"></pre>

JavaScript

var family = [
  {
    name: "Mike",
    age: 10
  },
  {
    name: "Matt",
    age: 13
  },
  {
    name: "Nancy",
    age: 15
  },
  {
    name: "Adam",
    age: 22
  },
  {
    name: "Jenny",
    age: 85
  },
  {
    name: "Nancy",
    age: 2
  },
  {
    name: "Carl",
    age: 40
  }
];

function printUniqueResults (arrayOfObj, key) {
  return arrayOfObj.filter((item, index, array) => {
    return array.map((mapItem) => mapItem[key]).indexOf(item[key]) === index
  })
}

const result = printUniqueResults(family, 'name')
document.getElementById('result').innerHTML = JSON.stringify(result)