*{
    box-sizing: border-box;
}

body{
    background-color: aquamarine;
}
#padre{
    width: 90%;
    height: 300px;
    margin: 10px auto;
    background-color: blue;
    padding: 16px;
    display: flex;
    justify-content: center;
}

#hijo{
    width: 100%;
    height: 268px;
    background-color: rgb(143, 219, 245); 
    padding: 16px;
}

#nieto{
    width: 100%;
    height: 236px;
    background-color: rgb(255, 0, 0); 
    padding: 16px;
}
#biznieto{
    width: 100%;
    height: 204px;
    background-color: rgb(164, 6, 255); 
}