Kesari and Anjana had in total 5 sons out of which Lord Hanuman was the eldest one. The names of other sons of King Kesari were: 

 1. Matimaan
 2. Shrutimaan
 3. Ketumaan
 4. Dhritimaan

Also, unlike Lord Hanuman, these all were married and had kids. All this is mentioned under Brahamand Purana. Apart from other things, this purana also contains the details of the family tree of Kesari and about other things in the life of Lord Hanuman. 

Following extract from Brahamand Purana verse 223 to 230 shows the same:

[![enter image description here][1]][1]

However, as per another website article listed in following links, it was mentioned that Lord Hanuman has one more brother called 'Gatimaan'. Although, they also mentioned their source as Brahamand Purana, but I am not able to currently find his details.
 
 - [Link 1][2]
 - [Link 2][3]

Also, link of Brahamand Purana can be found in this [answer][4]. The verses stated above can be found in Book 2 of the series.


  [1]: https://i.sstatic.net/tMFo3.jpg
  [2]: http://hindi.speakingtree.in/slideshow/hanumanji-ke-paanch-bhai-bhi-the/%E0%A4%AC%E0%A5%8D%E0%A4%B0%E0%A4%B9%E0%A5%8D%E0%A4%AE%E0%A4%BE%E0%A4%82%E0%A4%A1%E0%A4%AA%E0%A5%81%E0%A4%B0%E0%A4%BE%E0%A4%A3-%E0%A4%95%E0%A5%87-%E0%A4%85%E0%A4%A8%E0%A5%81%E0%A4%B8%E0%A4%BE%E0%A4%B0
  [3]: http://hindi.speakingtree.in/slideshow/hanumanji-ke-paanch-bhai-bhi-the/%E0%A4%B8%E0%A4%AC%E0%A4%B8%E0%A5%87-%E0%A4%AC%E0%A4%A1%E0%A4%BC%E0%A5%87-%E0%A4%A5%E0%A5%87-%E0%A4%AC%E0%A4%9C%E0%A4%B0%E0%A4%82%E0%A4%97%E0%A4%AC%E0%A4%B2%E0%A5%80
  [4]: http://hinduism.stackexchange.com/a/6751/1018