There are two issues you will need to address:
However you have provided no evidence of [your wife's] current immigration status.
This means they need to see documentary evidence that your wife is legally in the UK, and will be for the time you are visiting. You will probably need to provide copies of her passport and visa.
However the letter provided makes no mention of your leave being approved.
You need to get your employer to write you a letter saying that your 3 months leave has been approved, giving the dates, and send it with your next application.
You have stated in your application that you wish to visit your spouse and cousins for a period of 3 months and 22 days.
You need to make sure that the dates you have proposed for your visit agree with the dates that your employer has approved for your leave. If your employer grants you 90 days leave, your visit schedule must allow you to return to the job before 90 days. It's possible that this is just an error by the processing officer, but you should make doubly sure you are clear about your itinerary in your next application.
Since no mention is made of finances I assume that the documents your provided satisfied them. You will have to explain how you can take 90 days away from your job and still afford to travel.