proof of address for Tier1 spouse for ILR application

Hi

i am on tier 1 general and my 5 years will be completed in the month of july 2015,My wife came to UK as Tier 1 General dependent/spouse in Feb 2012 and we got tier 1 Extension in November 2012,as far as i know for ILR application main applicant and the dependent/spouse must provide proof of living at same address for two years.in short my wife used her sister's address for all documentation like,Bank account,nhs,dvla,NI etc in case we relocate to other address.From October 2013 all document related to my wife have been updated to our current address with addition of Electrol Role,through out that period my address remain the same(current one)

if i apply for ILR for myself and my wife we can not provide documents to proof we live at same address for last two years(it will be 20 months in July 2015),how can i cover it up?
**(My child born in October 2012 and birthday certificate has both of us names and our current address as a temporary address on it)

Any advice or suggestion please??
Thanks in advance!!!!
Regards
Mian Ali

Explain in the cover letter why you had separate addressees. You have a child together and this is a proof of genuine relationship. Pictures together, witness statements from friends etc. Do not lie and do not make up stories. You should be fine.