So my first questions are: is the above doable by a non-programmer? 
What you are trying to accomplish is not an easy task. it will require a decent understanding of relational databases and how to set them up.
Sure it is doable by a non programmer as long as you are willing to learn about relational databases and are not tied to a strict deadline, if you are tied to a strict deadline, then it would be a good idea to get help in setting this up through the job board
How do I distinguish Member1 from Member2 (in the same record) for the login setup?
Here's where we start to get into relational database design. the two users will need to be in separate records.
the users personal information would be stored in a users table.
any information that can be shared by two users would be stored in a separate table.
in this case, you can have household memberships where both users share the same address. The address information will be stored in a separate table the users table will have a foreign key column to create the relation ship between the user record and the address record.
What other suggestions can you give me?
Read up on relational database design, there are a number of good books on MySQL and PHP , most of them will have chapters that explain the database structure, then give step by step on developing the PHP to use that database structure.
look through the bookstore shelves to find one that goes through creating a membership site, try and find a few of them, and find the one that matches what you are trying to accomplish closest.
