CSS - Make an item start in the middle of previous row

Question

I'm trying to use CSS Grid to have a div that starts in the middle of the div in the row above. I want both divs to wrap around the text. This is what I'm trying to achieve:

As you see on the picture, in some cases, the subtitle might be longer than the title, and sometimes not.

I tried different ways but I can't figure it out. Here's my last attempt. The problem here is that (of course) the "Title" div becomes wider as the subtitle is longer.

#container{
  border:solid black;
  display:grid;
  grid-template-columns: max-content auto;
  grid-template-rows:1fr 1fr;
}

#title{
  border:solid blue;
  grid-column:1/2;
  grid-row:1/2;
}

#subtitle-container{
  border:solid red;
  grid-column:1/2;
  grid-row:2/3;
  
  display:grid;
  grid-template-columns:50% max-content;
}

#subtitle-text{
  border:solid green;
  grid-column:2/3;
}

<div id="container">
  <div id="title">Title</div>
  <div id="subtitle-container">
    <div id="subtitle-text">This is a rather long subtitle
    </div>
  </div>
</div>

Answer 1

Here is an idea where you can create a hidden float element that will push the subtitle. You simply make the float element 50% width of the title and you need to make the width of the title fit-content.

.container{
  border:solid black;
  margin:5px;
}

.title{
  border-bottom:solid blue;
  width:-moz-fit-content;
  width: fit-content;
}

.title:after {
  content:"";
  float:left;
  width:50%;
  height:2px; /*not needed*/
  background: red; /*not needed*/
  margin-top:10px; /*need to be a small value*/
}
.subtitle-text{
  border:solid green;
  display:inline-block;
}

<div class="container">
  <div class="title">Title</div>
  <div class="subtitle-text">This is a rather long subtitle</div>
</div>

<div class="container">
  <div class="title">Long long Title</div>
  <div class="subtitle-text">Subtitle</div>
</div>

<div class="container">
  <div class="title">Very Long long Title</div>
  <div class="subtitle-text">Subtitle</div>
</div>