Hi Fiona
I had a look at Stradbroke parish register but couldn't find a baptism for Francis. A John and Anne Keeble were baptising children in the parish at this time: John 7/11/1830, Ann 16/9/1832 and Sarah 4/5/1834.
I looked prior to 1828 but couldn't see a Francis at all. Also no marriage at Stradbroke for John and Anne.
A John Keeble married an Ann Howard of Linstead Magna at Linstead Parva on 3rd March 1828.
Both signed X, witnesses George Howard and Lucy Howard, both signed X.
Banns 17 Feb, 24 Feb, 2 March 1828
I checked baptisms at both Linstead Magna and Linstead Parva 1828-1830 in case Francis Keeble had been born to this couple in a different parish but the baptism wasn't there either.
Not sure if this is any help or not