Get selected xml tag in netbeans platform editor cookie

I am developing a netbeans platform application and I have a custom xml editor. The xml document looks similar to this one (This is an example):

<paragraph id="1">
    <sentence id="1">
        <word id="1">Hello</word>
        <word id="2">World</word>
        <word id="3">.</word>
    </sentence>
    <sentence id="2">
        <word id="1">This</word>
        <word id="2">is</word>
        <word id="3">another</word>
        <word id="4">sentence</word>
        <word id="5">.</word>
    </sentence> 
</paragraph>
<paragraph id="1">
    <sentence id="1">
        <word id="1">New</word>
        <word id="2">Sentence</word>
        <word id="3">.</word>
    </sentence>
    <sentence id="2">
        <word id="1">Test</word>
        <word id="2">two</word>
        <word id="3">.</word>
    </sentence> 
</paragraph>

Now the user wants to select the second sentence of the first paragraph. Here he clicks on the line of the second sentence and with a right click the "implemented" action will be executed.

I have the following code so far: In the first code snippet, I get the xml structure and the complete DomDocument. But I have no access to the selected line.

    private final EditorCookie context;

The following is executed in the actionPerformed-Method:

CloneableEditorSupport editorSupport = (CloneableEditorSupport )context;
    try {
        InputStream inputStream = editorSupport.getInputStream();
        InputSource inputSource = new InputSource(inputStream);
        Document xmlDoc = XMLUtil.parse(inputSource, true, true, null, new RegisterCatalog());

        NodeList nodeList = xmlDoc.getElementsByTagName("sentence");
           ...

And in the second code snippet, I have access to the selected line:

JEditorPane[] panes = context.getOpenedPanes();
if (panes != null) {
    if (panes.length > 0) {
        JEditorPane pane = panes[0];

        AccessibleContext ac = pane.getAccessibleContext();
        AccessibleText accessibleText = ac.getAccessibleText();
        int caretPosition = accessibleText.getCaretPosition();

        StyledDocument document = context.getDocument();
        Element characterElement = document.getCharacterElement(caretPosition);
        int start = characterElement.getStartOffset();
        int end = characterElement.getEndOffset();
    }
}

With the start and the end position I get:

<sentence id="2">

But what I want is with a right click on the line of the second sentence

I want to get:

<sentence id="2">
    <word id="1">This</word>
    <word id="2">is</word>
    <word id="3">another</word>
    <word id="4">sentence</word>
    <word id="5">.</word>
</sentence> 

Is there a possibility to access the whole tag including its closing tag? Another problem is the comparability of the lines because with

<sentence id="2">

I cannot uniquely identify which one is selected because there are two sentences with the id="2" and I need to distinguish which one is selected. I hope you can help me :)