I agree with the birth entry for son Francis, and he was baptised 30/4/1843 Bryanston Sq. St Mary, Westminster, son of John Mills, brass founder, and Mary.
I can find children born to John, brass founder, and wife Mary before then but they don't tie in with the 2 daughters shown on 1851 - cannot find a daughter Jane bc.1841, and although they had a daughter Emily she wasn't born until 1839 (confirmed with birth index) and bp.13/10/1839.
Things just not tying up here.
Annette