I would put money on the Ottaway Street family being the correct one, and the baptism found by Bookbox is him.
Just to clarify ...
I posted the 1882 baptism simply to
link up the records that have been found for William Robert Kent -- birth index (reply #23) and 1891 census in Ottaway Street (reply #25) -- NOT because I think he is the right person. He has the wrong father (James) with the wrong occupation (labourer/carman), as compared to the 1909 marriage record.
However, the Willie Kent in Peacock Street, Bethnal Green (reply #17), has the right father (John) with the right occupation (cabinet maker). Admittedly he apparently has no brother Charles, but with the greatest respect it's possible that the details of this WW1 death, or the brother's name, may have been misremembered over time.
This William Kent in Peacock Street with the father John (cabinet maker) is said in 1891 to have been born in Whitechapel 1885/86. Perhaps he just
thought he was born in Hackney? Peacock Street is in any case very close to the parish boundary with Hackney. Just a thought.