A bit of slogging through the census material might help. For example there are only 8 Robert listings aged 6 or less in the 1851 census. I had a quick look at a couple of them.
Robert aged 1, living with gradparents Charles & Elizabeth Howland in Bride. He was the illegitimate son of Elizabeth Howland and had a half sister Catherine Caley and half brother Thomas Sayle. With his mother in '71.
Robert aged 3 son of Enos & Catherine living in Michael. He appears to be married in th 1881 census.
Some others:
aged 1 son of Robert & Ann in Andreas. With parents in '61
aged 1 son of Ewan & Ann in Andreas
aged 3 son of William & Ann in German
aged 4, nephew to Catherine Boyde in German
aged 5, son of John & Elizabeth in Andreas, possibly married in 81
aged 6, son of John & Jane in Andreas