In the sentence:
He just called me to confirm everything with his father and also they have selected which company they will contact
"he" is a third person pronoun and "his father" is the father of "he". So "they" is "he & his father". What troubles me is the preposition "with" in this context. Does it mean: he called me to confirm everything together with his father, or does it mean that his father also confirms everything?
The sentence
He called me to confirm everything with his father.
can have several meanings. In this case, either it means that his father has confirmed everything and he is reporting this to "me", or that he and his father together are confirming everything.
It could also have meant that "I" am acting as an agent for his father, and he is telling "me" to tell his father that he confirms everything.
He just called me to confirm everything with his father
I read this a little differently.
The person "He" called the speaker ("me") to confirm that something he had some previous knowledge of that has to do with his father was true/accurate. Or, alternatively, that the father had told the "he" to call the speaker ("me") to call "he" and confirm something the speaker "me" and the "father" had discussed previously, I would think?
If the person "He" and the person "father" had called together, the more normal way of writing it would be "He and his father" or "along with his father, he", or even "with his father he", because most english speakers don't use a "with" to mean "a person with another" after using the word confirm as the meaning shifts due to the confirm/with structure.
This sentence has several faults that can't be excused by imagining some contrived context.
"with" would never [1] be valid here - a reasonable alternative would be "concerning".
"and" doesn't work unless followed by something like "to say".
"also" is clumsy here and should probably be discarded unless the whole sentence is recast.
"they have selected" should probably be preceded by "that".
Apart from basic grammar errors, there's a fundamental problem regarding exactly the scope of the word "confirm" here. I doubt OP really intended it to include confirming the company selection, because in that case I can't see why he'd ever have included the word "also" in the first place. But if that were to be the intention, one valid phrasing might be...
He just called me to confirm everything concerning his father, including the fact that they have selected which company they will contact.
If on the other hand "confirm" covers only some other details already known to need confirmation, and the matter of company selection is simply some additional piece of information passed across in the context of the call...
He just called me to confirm everything concerning his father, and to say [that] they have selected which company they will contact.
[1] You could feasibly justify "with" here if the father was actually with the speaker at the time, and "he" was calling the speaker's number in order to get through to his father, but I think this is hopelessly contrived.
