I'm reaching here, and may be way off base, but I'm intrigued with the name Minnie.
You posted in a different message that John'swife was Grace.If you are sure of this, then read no further.
I am trying to research a maternal line in my family, where I have a Minnie E. Chiquoine married to a "Vansyckel" in Philadelphia in 1888.I have not yet obtained the full marriage record.Her grandmother and sister were named Mary.Is it conceivable that she is the mother of Mary, Minnie, and Grace Van Sickle?The range of birthdates would be reasonable.Relocation from Philly to Fayette Co. is not unthinkable either.
Otherwise, I am somewhat surprised that there does not appear to be an established Van Sickle family of that era in Philadelphia, based on what I can skim here on this forum.
I will try to obtain the marriage record soon.Let me know if this is of interest.