Joe Biden's Mum and the importance of commas

Can you see something wrong in this recent Daily Mail headline?

Joe Biden's mother who was of Irish descent 'hated' England so much that she chose to sleep on the FLOOR rather than in a bed where the Queen once stayed, new book reveals

When I read the line 'Joe Biden's mother who was of Irish descent "hated" England...', I immediately thought, 'What about Joe's other mother?' Why? Because the writer has forgotten to put in the commas around 'who was of Irish descent'.

If you want to add information to a noun or pronoun using a relative clause, you have to decide whether the information is essential or non-essential. Look at these further examples:

1. Officer! The boy who stole my phone is over there.

2. Dean Smith, who is an ugly bastard, stole my phone.

In the first case, the part in red is essential. It defines who I am talking about and without it - 'Officer! The boy is over there!' - the police officer would wonder what I wanted and ask, 'Which boy?' When information is essential, there is no need for commas around it. You may also see 'essential' clauses referred to as 'defining' or 'restrictive' clauses.

In the second case, the main point is that Dean Smith stole my phone. The bit in red is non-essential and, you could argue, a matter of opinion. Even without this piece of information, the sentence would make sense. When information is non-essential (or 'non-defining' or 'non-restrictive', you DO need commas around it to set it apart from the main sentence.

So, coming back to the article about President Joe Biden, from a grammatical point of view the sentence 'Joe Biden's mother who was of Irish descent hated England...' has an essential clause defining Joe Biden's mother as 'the one who was of Irish descent', which immediately makes you think, 'What about the other one who is not of Irish descent?', something that is both rude and impossible. Come on, Daily Mail, get it right!