When I saw the "emo/intellectual type" I instantly thought of a giftcard to Warby Parker for some new hipster specs Or maybe some craft beer and an Amazon GC?
My brother is 25 and just moved out ... he asked for touchscreen gloves, a down comforter, and Dove Men's bath products (lol). In the past I've also given him liquor and gift cards to restaurants, StubHub, and Amazon.com. Would he like anything on ThinkGeek.com?
For the SIL ... I agree with the restaurant gift card, especially if you can offer to babysit the kids while they go out. What about a big basket with household items (paper towels, cleaning supplies, etc.) so that their grocery money can just go toward food? Or a gift card to get her nails done so that she can pamper herself a bit?