If the net rental income for either of the properties exceeds €3,174 then that person has to register as self-employed using a form TR1 as that person is then deemed to be what's called a "chargeable person" by Revenue.
Then you will have to submit a Form 11 under that person's name and include all income (husband's & wife's) together on this form. Your husband then does not have to submit a Form 12 at all as the details have been submitted using the Form 11
So for example, if your net rental income for 2014 is €5,000, you have to register as a chargeable person for 2014 and submit a Form 11 to Revenue under your name. This Form 11 will include ALL income (rent, employment income, etc) for both yourself and your husband for the 2014 tax year
If the net rental income for either of the properties does NOT exceed €3,174 then the Form 12 will suffice for all income.