There are two generations of Robert Knowells.
One who married Ann Key in 1811 or 1813 and their son who was christened on Oct 24 1813.
He may have married Maria Matilda Cubbon in 1838

Note that when you see the following message on an IGI record, you know that this is not a transcription but a submission to the IGI.
Record submitted by a member of the LDS Church. The record often shows the name of the individual and his or her relationship to a descendant, shown as the heir, family representative, or relative. The original records are not indexed, and you may have to look at the film frame-by-frame to find the information you want. A family group record for this couple may be in the Family Group Record Collection; Archive Section. (See the Family History Library Catalog for the film number.) These records are alphabetical by name of the father or husband.

They are often (Frances might say "generally") wrong.
The record below the one you saw is a transcript. It has the following:
Messages:
Extracted birth or christening record for the locality listed in the record. The source records are usually arranged chronologically by the birth or christening date.
Note that in the 1841 census the two Roberts appear to me on the same page Robert Jr. 27 is next to a 24 year old Marsha (sic) Knowel and a 1 1/2 year old John. John Thomas Nowall was christened on Aug 11 1839, son of Robert Newall and Matilda Cubbon.