I noticed that last night as you know, but didn't have enough brainpower left to remember to look for Augustus. It's not uncommon for some children to be born illegitimately before the mother marries (and husband may or may not be the father). Oddly, I can't seem to find a birth for Augustus under Howard or Keeble. The 1871 census shows a daughter Sarah 1854, Augustus 1856 and John 1858. I'm unsure if Frank 1862 is before or after the marriage as I can find births in the same quarter for both surnames! With a succession of children like that though, rather than one or two illegitimates, if the marriage of Francis to Lucy Howard is right, I'd suspect either that Francis is the father and they just married late, or that Francis was married before and Lucy is not the mother of those children.*
Francis who is with his grandmother (1851) is also with John c1831 on that census. John on the previous census (1841) is with Ann and younger siblings Sarah (c1834), Lucy (c1836), and Charles (c1838). That's not to say James 1820 and Syer 1826 are not his siblings as well though... unfortunately again, no christenings.
* Edit-
Albert Augustus HOWARD b. Apr 1856, ch. 25 Feb 1857, Stradbroke, mother Lucy HOWARD (no father).
Annoyingly, this is the only child I've been able to find. They like to make it difficult, your lot, don't they?
Another edit-
It is interesting to note that (if I’m following the right guy) James 1820 is, in 1851, living with one Virtue KEABLE 1773 Thrandeston, who is a widow. It’s unclear what relation she is to him, as she’s been listed first in the household and then him second as the Head!
As for Syer (I'm not sure where 1826 came from, as the only census guy I could see of that name matches this) this could well be him-
Syer Keable
England Births and Christenings, 1538-1975
christening: 20 April 1817 WINGFIELD,SUFFOLK,ENGLAND
father: Charles Keable
mother: Phyllis