AA/PIP and Pension credit

Please help me about a question in Pension credit form does Applicant and /or partner
looks after somone receiving PIP or AA for 35 hours a week ?.
If one of the partners receives AA and the other PIP (both standard rate) and only they look after each other all the time . There is no carer ,no one else gives care to any of them , is yes to be ticked ? .
what is the relevance of this question ?

Thanks for reply, Gordon . So it t may be about SDP . I tried to understand but it is very complicated for me. It seems to me even if we meet the SDP criterion by one of us being on AA and other on PIP ( both standard rates ) and we have not worked for over a year yet claim no other benefit , we have no carer and no one looks after us except each other , we may not get SDP part . We still seem to have to meet a further condition of no Non Dependant relative living in the same property ( which is rented by both together) . .
I do not understand the underlying reason of no SDP altogether, if Non Dependant Relative do not pay our share of rent or expenses .Moreover they have a family and would need any time left from work to look after needs of their family / child care needs . They have anyway little time left for household chores as they work 6 days a week including some days overtime .
So why should it cause no SDP for me and my partner because of a housing situation even if we could be otherwise within the criterion ? am I missing something?
Regards

I dont know if asking more questions about pension credit is permissible here . But I am new to how benefits system works so I hope shall be excused .
On change of Rules to pension credit from 15 May this year , like many other couples who were previously not claiming it we also claimed in July retrospectively from May. It was approved mid August obviously all required information evidence provided with Application form .
My Question is how often are the reviews done . For example are there home visits evey one or 2 months to check self emplyed income if any previous years accounts and amount of savings ? Why previous year self employment accounts ? my claim is because of present income if any, as given in application form in July even if I had any income last year it would be irrelevant though I had none . Do any small changes to savings eg because we received pension credit arrears are to be taken as change of circumstances to be reported every month then ? is it such a headache to be faced so often . And should they not simply write a letter or email to ask for any information they may need for some reason ? why home visits after making a call on mobile only a day before ? How could I get annual accounts in day from the accountant . I am confused . Please advise
Zaib