Suppose I love someone so much, but cannot marry him. Now I've decided to marry another person, as per my parents wish, and I'm loyal to my husband fulfilling all his demands and obedient. But I'm still in love with the previous person in my heart. So can I ask him in my dua that I get his name in life after death? I want to be with him in jannah. Is this dua valid?
I am not sure but I assume such dua won't be accepted. If you love him, then why don't you ask your parents that you like him? During the time of the prophet, Ali used to like Fatima but he never expressed it. But the prophet understood that and got him married to Fatima. Islam doesn't prohibit you to propose to someone or like someone without sinning.
If you are going to marry someone else but have that man in your mind then you will never be happy with him. How can you allow someone whom you don't desire to have physical relations with you? This would create many problems in your life.
[I think my response needs more elaboration. I would be grateful if someone suggests something good to add in my answer (in comments). Thanks.]