Julius Caesar was married to Calpurnia, but Portia was married to Marcus Brutus, not Marc Antony. I don't see why you feel you need to prove that both these men loved their wives, since there is no suggestion in Shakespeare's play that they did not.
There is a long conversation between Brutus and Portia in Act 2, Scene 1, in which it is clear that they have a very close relationship. At one point Brutus says:
You are my true and honorable wife,
As dear to me as are the ruddy drops
That visit my sad heart.
The text does not contain as many interchanges between Caesar and Calpurnia as between Brutus and Portia, but Capurnia's deep concern about her husband shown in Act 2, Scene 2, in which she tries desperately to persuade him to stay at home on the Ides of March, certainly proves her great love for him. This suggests that they have a loving relationship, although Caesar is not as free about expressing his feelings as Brutus, Portia, or Calpurnia.