tsql : is it possible to do nested case statements in a select?

how do i incorporate a nested if statement in a select clause of a sql query? I know to use case when condition then X else y end but how do you do a nested one in the same fashion for each record in a record set.

if x.boy is not null then 
   x.boy 
else if x.girl is not null
   then x.girl 
else if x.dog is not null 
   then x.dog
else 
    x.cat 

here is my attempt:

SELECT top 10
        id,
        case when x.boy <> NULL then 
            x.boy
        else case when  x.girl <> NULL 
            x.girl
                else case when  x.dog <> NULL 
            x.dog
                else x.cat 

        end as Who 
from house x

is this correct?