Android isn't my area of expertise. There are people on this site who have made my mods compatible with android versions before though.
I think she shouldn't say "my William", but rather "my father" or "my dad". The same goes for Chloe, who calls Janet by her name instead of mother/mom. In the game files there are some variables for their parents, pa_name for William and ma_name for Janet. I tried to change it, but it worked for the MC too, so he would call William father.
Devil's advocate: the important point is the "my" in "my William". Let's say your landlord/boss/whatever is named "Teddy": will you call him "MY" Teddy? Obviously not, you'll call him simply "Teddy". Using such a wording, with a possessive pronoun, suggests that there is a strong and close relation between the two - I say "MY son", "MY wife", "MY parents", "MY brother", etc., like everybody. I think we both agree on this point of showing a close bond?
Here you go :
