How to have multiple same start tags but single end tag?

Question

So I have an .XML file which has a start tag

abc "some text">  <abc "some text" > </abc>... 

This means two same start tags, but one single end tag...
How's this possible?

Answer 1

It's not possible, it's invalid markup.

Every tag has to be closed in XML!
(Except for processing instructions - which are not considered to be "tags").

Answer 2

All start tags must have matching end tags in XML. Your textual data is not XML if this property is untrue.

Note that your example has two other problems:

1. The < on the first abc opening tag is missing.
2. "some text" must be preceded by an attribute name and an = character.

So, this would be well-formed (meets the requirements for being XML):

<abc d="some text">  <abc d="some text" > </abc></abc>

For further details on what well-formed means, see Well-formed vs Valid XML.