He doesn’t like his wife to visit her family when her male cousins are there
Question

                My question is regarding my wife. When she goes to visit her parents in their house, sometimes her male unmarried cousins stay the night in the same house. In these situations, I prefer to stay with her in her house and do not like her staying alone, even though our son, about 4, also stays with her and she does sleep in a separate room. 

Am I right to prohibit her from staying in her parent's house when this condition is not fulfilled (that is, I cannot stay the night with her, while the cousins do). Is this from Shariah or is this prohibiting what Allah has made lawful. Also, please note that I feel extremely uncomfortable about this situation, though my wife keeps telling me I should be more trusting. 

Another question is related as well. Is it right to prohibit my wife from travelling for pleasure and sight-seeing with her family when she is accompanied by her parents and brother but also the unmarried male cousins. Please note that I don't mind this when I'm around. But is it ok when I'm not with my wife. Again, I feel extremely jealous when this happens as I feel I should be the one taking her around and not any stranger, even if she's accompanied by her parents and brother. Can you please, again comment on whether this is normal or goes against the allowance given in the Shariah.
Praise be to Allah.Firstly: I would like to remind you of what 
    the Messenger  (peace and blessings of Allaah be upon him) said: “I have not left behind me any fitnah (temptation) that is more harmful to 
    men than women.” (Narrated by al-Bukhaari, 4808; Muslim, 2740, from the hadeeth of Usaamah ibn Zayd). 
Secondly: It is permissible for a woman to be 
    in her father’s house when there is a non-mahram present, so long as there is no fear of haraam mixing or of the fitnah (temptation) that may 
    happen as a result of that. 
But if there is no guarantee that there will 
    be no mixing and no fitnah, then that is not permissible. It is even more haraam if the woman does not observe proper Islamic hijaab. 
Thirdly: a boy of four years of age is not 
    considered to be a mahram because the role of a mahram is to guard and protect the woman, and this cannot be done by a four year old child. So it 
    makes no difference whether this boy is there or not. 
Fourthly: if your wife’s father and brothers 
    take this man’s presence lightly and do not care if he is alone with your wife or if she takes off her hijaab in front of him, then it is not 
    permissible for you to leave your wife with them, because they are careless about protecting their daughter. The Prophet  (peace and blessings 
    of Allaah be upon him) said: “Beware of entering upon women.” A man from among the Ansaar said: “O Messenger of Allaah, what do you think of the 
    in-law?” He said, “The in-law is death.” (Narrated by al-Bukhaari (4934) and Muslim (2172), from the hadeeth of ‘Uqbah ibn ‘Aamir). So you must 
    protect your wife and feel protective jealousy and pride (gheerah) where she is concerned, and not expose her to temptation. 
Fifthly: With regard to her going on trips, 
    there is nothing wrong with that if the place to which she is going is not one where immoral people meet, such as beaches and other places which 
    are very dubious, and so long as she will keep her hijaab on and stay far away from places of temptation. If you are worried that the presence of 
    that non-mahram man will be a cause of fitnah or may make her do something that Allaah has forbidden, then you must not allow your wife to travel 
    with them. This is the matter of praiseworthy protective jealousy (gheerah) that is loved by Allaah and His Messenger. If a man feels protective 
    jealousy towards his family he will stop them from committing immoral actions and anything that may lead to that. 
You should note that most of the disasters 
    that befall families come from friends or relatives, so try your best to protect your wife from that. 
And Allaah knows best.