Automatic alignment between text below nodes in FlowChart

Question

This is my first TikZ diagram. I want to get the Figure like this

I use this code

\documentclass{article}
\usepackage[latin1]{inputenc}
\usepackage{tikz}
\usetikzlibrary{shapes,arrows}
\begin{document}
\pagestyle{empty}
\tikzstyle{line} = [draw, -latex']
\begin{tikzpicture}
\node [draw,rounded corners, fill=blue!20] at (2,1) (Start) {Some Text};
\node [draw,rounded corners, fill=blue!20] at (0,0) (Block1) {Text Text};
\node [draw,rounded corners, fill=blue!20] at (4,0) (Block2) {Text};
\node [draw,rounded corners, fill=blue!20] at (6,0) (Block3) {Text Text Text};
\node[text width=3cm] at (0,-1.5) {some text spanning three lines with automatic line breaks\\
Another line of text};
\path [line] (Start) -| (Block1);
\path [line] (Start) -| (Block2);
\path [line] (Start) -| (Block3);
\end{tikzpicture}
\end{document}

• Placement of node and related text below nodes.
• Equal distance between text below nodes.
• Make this diagram at Center of the page.

Edit: After getting the answer, I am wondering if I want the diagram as

Answer 1

Since my answer to a later question by Diaa Abidou apparently answered this one possibly better, I am repeating that answer here for completeness. For a full explanation of the code, please see the details I provided there.

\documentclass[border=10pt,multi,tikz]{standalone}
\usepackage[edges]{forest}
\usepackage{calc}
\usetikzlibrary{arrows.meta}
\forestset{%
  declare dimen register={gap},
  gap'=20mm,
  declare dimen register={lbox width},
  lbox width=(\textwidth-2*\forestregister{gap})/3,
  rbox/.style = {draw=blue!80!black, fill=blue!20, rounded corners},
  lbox/.style = {align/.wrap pgfmath arg={@{}p{##1 pt}@{}}{(lbox_width)}},
}
\begin{document}
\begin{forest}
  forked edges,
  for tree={%
    font = \sffamily,
    edge = {draw, -{Latex}},
  },
  where n children=0{%
    lbox,
    no edge,
  }{%
    rbox,
  }
  [Some Text, name=Start, l sep+=5pt
    [Text Text, name=Block1
      [1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
      ]
    ]
    [Text, name=Block2
      [1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
      ]
    ]
    [Text Text Text, name=Block3
      [1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
      ]
    ]
  ]
\end{forest}
\end{document}

EDIT

In response to a query asking how to reduce the distance between the terminus nodes and their parents, I would change the value of l for those nodes. However, we need to delay this until after the tree is packed in order to override Forest's calculations.

For example,

  where n children=0{%
    lbox,
    no edge,
    before computing xy={%
      l'-=10pt,
    },
  }{%
    rbox,
  }

produces

\documentclass[border=10pt,multi,tikz]{standalone}
\usepackage[edges]{forest}
\usepackage{calc}
\usetikzlibrary{arrows.meta}
\forestset{%
  declare dimen register={gap},
  gap'=20mm,
  declare dimen register={lbox width},
  lbox width=(\textwidth-2*\forestregister{gap})/3,
  rbox/.style = {draw=blue!80!black, fill=blue!20, rounded corners},
  lbox/.style = {align/.wrap pgfmath arg={@{}p{##1 pt}@{}}{(lbox_width)}},
}
\begin{document}
\begin{forest}
  forked edges,
  for tree={%
    font = \sffamily,
    edge = {draw, -{Latex}},
  },
  where n children=0{%
    lbox,
    no edge,
    before computing xy={%
      l'-=10pt,
    },
  }{%
    rbox,
  }
  [Some Text, name=Start, l sep+=5pt
    [Text Text, name=Block1
      [1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
      ]
    ]
    [Text, name=Block2
      [1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
      ]
    ]
    [Text Text Text, name=Block3
      [1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
      ]
    ]
  ]
\end{forest}
\end{document}

Answer 2

Try:

\documentclass{article}
\usepackage[latin1]{inputenc}
\usepackage{tikz}
\usetikzlibrary{arrows.meta,positioning}
\begin{document}
\pagestyle{empty}

\begin{figure}
    \centering
    \begin{tikzpicture}[
         font = \sffamily,
line/.style = {draw, -Latex},
  rbox/.style = {draw=blue!80!black, fill=blue!20, 
               rounded corners, inner sep=2mm,
               node distance = 12mm and 18mm},
lbox/.style = {text width=32mm, inner sep=0pt,
               node distance = 2mm}
                        ]
\node (Start)   [rbox] {Some Text};
\node (Block1)  [rbox,below  left=of Start] {Text Text};
\node (Block2)  [rbox,below=of Start]       {Text};
\node (Block3)  [rbox,below right=of Start] {Text Text Text};
\node [lbox,below=of Block1] {some text spanning three lines 
                              with automatic line breaks.

                              Another line of text};
\node [lbox,below=of Block2] {some text spanning three lines
                              with automatic line breaks};
\node [lbox,below=of Block3] {some text spanning three lines
                              with automatic line breaks.};
\path [line] (Start) -- coordinate (a) (Block2);
\path [line] (a) -| (Block1);
\path [line] (a) -| (Block3);
    \end{tikzpicture}
\caption{my figure}
    \label{fig-1}
\end{figure}
\end{document}

I assume, that image is in document placed in float figure. Inside it you can center it with \centering. If this is not a case, then you can use

\begin{center}
< your tikz image >
\end{center}

In above MWE I defined styles rbox for rounded nodes and lbox for nodes below rounded boxes. For their positioning I use relative positioning from library positioning.

Addendum: In case of image as show in edited question, you need to do some small changes:

• define coordinate (a) on the new way: \draw (Start.south) -- ++ (0,-6mm) coordinate (a);
• redefine node distance in rbox node style to something like node distance = 12mm and 0mm
• and, of course, delete block from code ...

\documentclass{article}
\usepackage[latin1]{inputenc}
\usepackage{tikz}
\usetikzlibrary{arrows.meta,positioning}
\begin{document}
\pagestyle{empty}

\begin{figure}
    \centering
    \begin{tikzpicture}[
         font = \sffamily,
line/.style = {draw, -Latex},
  rbox/.style = {draw=blue!80!black, fill=blue!20,
               rounded corners, inner sep=2mm,
               node distance = 12mm and 0mm},
lbox/.style = {text width=32mm, inner sep=0pt,
               node distance = 2mm}
                        ]
\node (Start)   [rbox] {Some Text};
\node (Block1)  [rbox,below  left=of Start] {Text Text};
\node (Block3)  [rbox,below right=of Start] {Text Text Text};
\node [lbox,below=of Block1] {some text spanning three lines
                              with automatic line breaks.

                              Another line of text};
\node [lbox,below=of Block3] {some text spanning three lines
                              with automatic line breaks.};
\draw        (Start.south) -- ++ (0,-6mm) coordinate (a);
\path [line] (a) -| (Block1);
\path [line] (a) -| (Block3);
    \end{tikzpicture}
\caption{my figure}
    \label{fig-1}
\end{figure}
\end{document}