With the weddings so close together, you should give him the same amount as he gave you, or as close as you can afford. The only exceptions would be (1) if your spouse can't attend his wedding, but his attended yours (then I'd say $250 would be appropriate), or (2) if you have to spend significantly more to attend his wedding than he spent on yours (ex. yours was local for him, going to his requires travel, hotel, etc. for you - in which case, I'd say $300 would be appropriate).
Congrats to you both!