His father chose a wife for him who he does not want
Question

                After being convinced for years by my parents to marry my cousin, I finally agreed last year and got engaged. I would however admit that I had no special liking for her and before I took the final decision, I also performed Istikharah but didnt seem to get a proper answer or direction and remained confused. I finally thought that since my parents are happy with this marriage I would go for it. I study in another country and after we got engaged I started talking to her on phone and among other things got to know that she has a problem of falling hair and due to that her hair has thinned a lot. I asked her to visit some doctors and she has started to take medications but not of any great help as of now. After knowing all this I am very upset with myself and also with her although I have not told anything like that to her that might hurt her in anyway. I really feel very upset all the time now as you would understand that I also have some feelings and wishes about how my future wife should look like. Right now I am always in distress and feel like that this is my destiny to marry her which cannot be changed as doing that would severly damage the relations in our family. I don't know what to do and can't stop thinking about this. This has now started to affect my studies also. I can't talk about this to anyone not my parents or friends. Thinking about this is always keeping me disturbed. I have agreed to marry her next year after my parents told me so. I don't know what to do now or how things would go after that. I would like to have your suggestions and guidance in this regard.
Praise be to Allah.Firstly:
Istikhaarah is mustahabb and is prescribed in Islam, but one does not necessarily see a dream after it or get an answer as you described. Rather its effects appear in the matter being made easy. If the matter is made easy and goes ahead, this is an indication that it is good, in sha Allah.
Secondly:
The son is not obliged to obey his parents with regard to marrying a particular woman, but if he does that to please his parents and make them happy, he will be rewarded for that, so long as the woman is religiously committed and of good character.
If he gives the matter some thought and decides that the woman is not appropriate for him, and is afraid that he will develop resentment towards her or that he will later be forced to divorce her, then it is better for him to tell his parents frankly about what he feels and to apologise to them for cancelling his engagement. This is better than going ahead with something he does not really want.
We advise you to think long and hard and to examine your fiancée’s characteristics, both positive and negative, before taking the decision to cancel the engagement. If she is religiously committed and of good character, and has no faults other than what you mention about her hair, then this can be dealt with. And a woman may be beautiful or acceptable despite that problem.
But we also think that you should delay going ahead with the marriage until you have put your mind at rest about that decision.
You should offer a lot of du‘aa’ (supplication) and ask Allah to guide you to that which is best in this world and in the Hereafter.
See also the answer to question no. 26852
And Allah knows best.