Find Ancestors

hi, i am very new to this. i am trying to trace members of my mum`s family , she was adopted in 1950 aged 10months old, we belive from old letters found that she had a brother called terence dean russell who would of been around 1-2 years old when she was adopted , it is belived that her birth mother and father were encouraged to have terence adopted as well , my mothers dearest wish would be to find her brother. the birth parents were john allen russell who is written at the time to be living in battersea london and ivy sarah hilda long( she also assumed the name russell at the time of the adoptions) who is written at the time to be living in islington london. there are two older sisters from a previous relationship on the fathers side who we have little information of . it would be great to hear from anyone who may be able to help. my mother brenda jean russell was born the 11th may 1949 registered in batersea london , her brother terence is belived to of been registered in wittam . my mother has traced a brother christopher and two sisters paula and sheila who were born much later on to the same birth parents,. please get in touch if you think you may have any information that may help i am always happy to recieve mail..........sara