In a sentence like this, how do you differentiate to whom the son belongs? I wasn't sure whether it was "his" son, or "his aunt's" son. I see now that it was "his" son, but how would the sentence look if the son belonged to the aunt?
The sin indicates that sønnen belongs to hans tante (the subject of the sentence). If the son was belonging to any man (even the one who grammatically possesses the aunt) it would be "Hans tante vil gerne ringe til hans søn"
Based on nothing but doing Duolingo for a couple and getting a sense of context from the provided examples, it seems to be "vil gerne" always means "would like [to]", while vil simply means "wants".
Confirmation from a native would be great though!