Okay, I just registered because of a few things. Philly area native here and just wanted to drop a few cultural reminders and tidbits on the line to maybe help out?
1) West Philly was a predominately Italian working-class neighborhood back in that day that Joseph would have been born. I know from friend's whose families have been in the area for years as well as those who have just moved here that when groups of people immigrate, there can often be clumps of people from the same areas coming to the same place because they have reported doing well from the US. That means that not only is there a tendency for Roman-catholic Italian families to have a lot of children (I am stereotyping forgive me) but they could also have cousins come which make an even wider net.
TL;DR - Like many others have said Zarelli isn't as uncommon as you think.
2) I worked in for a brief period as an assistant for a property management firm around my area and heard talk about was a property company/ construction company owned by a family named Zarelli doing work in DELCO. They were big property owners. BUT, it should also be said a lot of prominent families in the Philly area Italian because of the reason I listed above and how migration operates.
3) I also worked in record management for a while (dealing with East Coast records) and let me tell you: THEY ARE A MESS. Not only because they were largely neglected for the most part, but also because of the amount anti-immigrant sentiments that occurred and lack of care. "You said your last name was Zarelli?" "Si, Cierelli." "Great. Joseph Zarelli." A potentially poorly educated population and or careless note taker and BAM.
I hope some of this insight helped. (And that I didn't break any rules. :$)
Edit: Also, would it help to drop a transcript of the press conference somewhere?