Actually it looks like there might be some contradictions in the citations
Would you like to help clarify?
Here's a source to read
http://books.google.com/books?id=lzVx_z_c0wQC&pg=RA1-PA132&...
Studies in Thirteenth-Century Justice and Administration
By C. A. F. Meekings
Notes on the D'Abernon family
I found another couple of sources
http://books.google.com/books?id=Tj8GAAAAQAAJ&q=D%27abernon&... Surrey Archaeological Collections, Volume 5 (Google eBook) Surrey Archaeological Society, 1871 - Archaeology. Vol. 1-37, 39-52 include report of proceedings 1854/55-1924, 1929-1951. Surrey Archaeological Society. 1907. Page: 59,60
And more listed in the profile for Gilbert d'Abernon
There is a bit in the Visitations of Surrey
http://books.google.com/books?id=kKwKAAAAYAAJ&vq=Peverell&p...
I think we're missing profiles on Geni and that may help nail a time line better. And I suspect the actual father of Sir John d'Abernon the elder may not be known definitively and we'll need to make a judgment call on how to best present in Geni.
Assistance welcome.