This:

declare @people as table (

person varchar(20),

dob date

)

declare @SDate as date = '5/3/2013';

insert into @people(person,dob)

values ('Frank','3/20/1990'),

('Joey','12/31/2000'),

('Sue','2/6/2012'),

('Mary','4/1/2013'),

('Bil','5/3/2012'),

('Bob','1/1/2013'),

('Will','10/1/2012')

SELECT person,

dob,

case when datediff(month, dob, getdate()) - case when dateadd(month, datediff(month, dob, getdate()), dob) > getdate() then 1 else 0 end < 12

then cast(datediff(month, dob, getdate()) - case when dateadd(month, datediff(month, dob, getdate()), dob) > getdate() then 1 else 0 end as varchar) + ' Months'

else cast((datediff(month, dob, getdate()) - case when dateadd(month, datediff(month, dob, getdate()), dob) > getdate() then 1 else 0 end) / 12 as varchar) + ' Years'

end as age

FROM @people

WHERE case when datediff(month, dob, getdate()) - case when dateadd(month, datediff(month, dob, getdate()), dob) > getdate() then 1 else 0 end < 12

then datediff(month, dob, getdate()) - case when dateadd(month, datediff(month, dob, getdate()), dob) > getdate() then 1 else 0 end

else ((datediff(month, dob, getdate()) - case when dateadd(month, datediff(month, dob, getdate()), dob) > getdate() then 1 else 0 end) / 12) * 12

end between 4 and 144