YOU SAID:
His son is a duck and is also the sun.
INTO JAPANESE
彼の息子はアヒルであり、太陽でもあります。
BACK INTO ENGLISH
His son is a duck and a sun.
INTO JAPANESE
彼の息子はアヒルと太陽です。
BACK INTO ENGLISH
His son is a duck and a sun.
That didn't even make that much sense in English.