I have always been confused about this pattern.
I can't be the first person to forget to pay his taxes.
That was the 11th family member to have been killed.
He can't be the person to have committed the crime.
This pattern makes me confused about when I should use the who-clause and this pattern. Why are using to-infinitive here instead of adding the who-clause?
I can't be the first person who forgets to pay his taxes.
That was the 11th family member who has been killed.
He can't be the person who has committed the crime.
My second question: Are there situations in which the use of one of them is more appropriate than the other?
My third question: What grammatical concept does this particular pattern represent?