Create a multi choice field from a relationship

Hi All.
I need to create a multi choice field in table A that is pulling in all records from table B, and the user can choose from the records to be included in the field. Is this possible? If not, what is a good workaround for this functionality? 
I need to be able to see if a record from table B has any other secondary relationship to table A.
My initial thought was to create a sub-table for Table B, which was a self relationship, to pull in any other Table B records that were related to that record. This would then be pulled out and concatenated in the field of Table A. However, that is a lot of code, and API calls, and I would rather see if there is a different option.