Acting for Two or More Clients
According to rules 3.4-5 to 3.4-7 of the Code of Conduct you may jointly represent multiple clients provided that at the commencement of the retainer, you clearly advise each of the clients that :
you have been asked to act for more than one client in the matter;
no information received in connection with the matter from one client can be treated as confidential so far as any of the other clients are concerned; and
if a conflict develops that cannot be resolved, you will not continue to act for both clients and may withdraw completely from the file.
A lawyer who receives instructions from spouses or partners to prepare one or more wills based on their shared understanding of what is to be in each will should treat the matter as a joint retainer and comply with rule 3.4-5 (also see paragraph  of the commentary to rule 3.4-5).
Although not required by the rule, in some cases it is good practice to advise your clients to obtain independent legal advice before you accept a joint retainer. This is to ensure that the retainer is genuine and uncoerced. This may be especially relevant when one of the clients is less sophisticated or more vulnerable than the other. It is also good practice to avoid acting for more than one client when it is likely that a contentious issue will arise between the clients or their interests will diverge as the matter progresses. In any event, consent in writing, or a separate written communication to each client is required.
Even if all the parties consent, you should avoid acting for more than one client when it is likely that a contentious issue will arise between them.