I called St. Genevieve's rectory and asked regarding the boundries of their parish. The woman I spoke with explained that Church Road is one of their boundry lines. The number for the rectory is 215-836-2828. You might want to call for more specific information.
In working with a local realtor you should determine geographic boundries on your own and then provide your agent with those boundries. Agents are very good with working with geographic boundries such as, streets, zip codes, neighborhoods, townships, etc. We do not have the ability to access specific parish boundries - and, unfortunately, due to fair housing laws being the way the are - we are very hesitant to answer questions in that regard even if we know the answer. If you want to purchase a home in a specific parish - you should determine that parish's geographic boundries on your own and then provide those boundries to your agent. It is fine for an agent to look for homes for you within a defined geographic area that you provide. In that sense, you would say - we want a home in the Custis Woods section of Cheltenham - or we want a home on one of these streets.... or, you could even draw on a map for the agent and say we want a home in this specific area - then we can help you. But we could get ourselves in trouble by attempting to define your search for you by your telling us a specific parish that you want.
I hope this helps.