I had a friend do some digging for you on Ancestry - this is what she came up with....
I am sure that Walter and Emma Brown that was posted on genforum are the parents of Guy Petty Brown as they have one daughter named Elsie Petty Brown born 1897:
Walter Brown and Emma Petty were married Apr-Jun 1889 Brentford, Middlesex….. and it would seem that Walter died before the census 1911. As the census was taken on Apr 02 1911 and Guy was not born until Apr 04 1911 there is no way he would be recorded.
1881 England Census 1881 England Census Name: Emma Petty Age: 11 Estimated Birth Year: abt 1870 Relation: Daughter Mother's name: Emma Petty Gender: Female Where born: Louth, Lincoln, England Civil parish: Louth County/Island: Lincolnshire Country: England Street Address: 11 Little Lane Education: Employment status: View image Occupation: Scholar Registration district: Louth Sub-registration district: Louth ED, institution, or vessel: 14 Neighbors: View others on page Piece:3262 Folio:57 Page Number:12 Household Members: Name Age Emma Petty 39 Fanny Petty 15 William Petty 13 Emma Petty 11 Rose Petty 10 Elizabeth Petty 6 Kitty Petty 3
1901 England Census 1901 England Census Name: Walter Brown Age: 42 Estimated Birth Year: abt 1859 Relation: Head Spouse's Name: Emma Brown Gender: Male Where born: Dorking, Surrey, England Civil parish: Hanwell Ecclesiastical parish: St Mary and St Mark Town: Hanwell County/Island: Middlesex Country: England Street Address: Occupation: Condition as to marriage: Education: Employment status: View image Registration district: Brentford Sub-registration district: Acton ED, institution, or vessel: 26 Neighbors: View others on page Household schedule number: 221 Piece: 1205 Folio: 129 Page Number: 34 Household Members: Name Age Walter Brown 42 Emma Brown 32 Walter M Brown 11 Emma M A Brown 8 Edith M Brown 5 Elsie P Brown 3 Caroline L Brown 1
1911 England Census 1911 England Census Name: Emma Brown Age in 1911: 41 Estimated Birth Year: abt 1870 Relation to Head: Head Gender: Female Birth Place: South, Lincolnshire, England Civil parish: Hanwell County/Island: Middlesex Country: England Street Address: No1 Frederick Villas, Lower Boston Road, Hanwell, Middlesex Marital Status: Widowed Occupation: Domestic General Registration district: Brentford Registration District Number: 128 Sub-registration district: Hanwell ED, institution, or vessel: 7 Household schedule number: 111 Piece: 6860 Household Members: Name Age Emma Brown 41 Emma Brown 18 Elsie Brown 13 Carrie Brown 11 Dorothy Brown 5 Irene Brown 3 Albert Steptoe 27
Name: Elsie Petty Brown Date of Registration: Jul-Aug-Sep 1897 Registration district: Brentford Inferred County: Middlesex Volume: 3a Page: 115