I believe having the ability to relate contact to each other alone is not taking the functionality far enough. There should be support for creating a mail merge to a contact record and all its related contacts (i.e.. In the relationship tab). Currently creating a lookup from this tab does not include the original contact in the lookup. Even better would be the ability to choose which recipients are wanted in the mail merge and in CC or BCC fields. The usual Mail merge wizard but with an extra option to do the above would really work well as having the ability to add attachments etc. Is useful.